Usability Experts Unite: The Power of Heuristic Evaluation in User Interface Design

There’s no doubt usability is a key element of all great user experiences, how do we apply and test usability principles for a website? This article looks at usability principles in web design, how to test it, practical tips for success and a look at our remote testing tool, Treejack.

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A definition of usability for websites 🧐📖

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Web usability is defined as the extent to which a website can be used to achieve a specific task or goal by a user. It refers to the quality of the user experience and can be broken down into five key usability principles:

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• Ease of use: How easy is the website to use? How easily are users able to complete their goals and tasks? How much effort is required from the user?
• Learnability: How easily are users able to complete their goals and tasks the first time they use the website?
• Efficiency: How quickly can users perform tasks while using your website?
• User satisfaction: How satisfied are users with the experience the website provides? Is the experience a pleasant one?
• Impact of errors: Are users making errors when using the website and if so, how serious are the consequences of those errors? Is the design forgiving enough make it easy for errors to be corrected?

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Why is web usability important? 👀

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Aside from the obvious desire to improve the experience for the people who use our websites, web usability is crucial to your website’s survival. If your website is difficult to use, people will simply go somewhere else. In the cases where users do not have the option to go somewhere else, for example government services, poor web usability can lead to serious issues. How do we know if our website is well-designed? We test it with users.

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Testing usability: What are the common methods? 🖊️📖✏️📚

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There are many ways to evaluate web usability and here are the common methods:

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• Moderated usability testing: Moderated usability testing refers to testing that is conducted in-person with a participant. You might do this in a specialised usability testing lab or perhaps in the user’s contextual environment such as their home or place of business. This method allows you to test just about anything from a low fidelity paper prototype all the way up to an interactive high fidelity prototype that closely resembles the end product.
• Moderated remote usability testing: Moderated remote usability testing is very similar to the previous method but with one key difference- the facilitator and the participant/s are not in the same location. The session is still a moderated two-way conversation just over skype or via a webinar platform instead of in person. This method is particularly useful if you are short on time or unable to travel to where your users are located, e.g. overseas.
• Unmoderated remote usability testing: As the name suggests, unmoderated remote usability testing is conducted without a facilitator present. This is usually done online and provides the flexibility for your participants to complete the activity at a time that suits them. There are several remote testing tools available ( including our suite of tools ) and once a study is launched these tools take care of themselves collating the results for you and surfacing key findings using powerful visual aids.
• Guerilla testing: Guerilla testing is a powerful, quick and low cost way of obtaining user feedback on the usability of your website. Usually conducted in public spaces with large amounts of foot traffic, guerilla testing gets its name from its ‘in the wild’ nature. It is a scaled back usability testing method that usually only involves a few minutes for each test but allows you to reach large amounts of people and has very few costs associated with it.
• Heuristic evaluation: A heuristic evaluation is conducted by usability experts to assess a website against recognized usability standards and rules of thumb (heuristics). This method evaluates usability without involving the user and works best when done in conjunction with other usability testing methods eg Moderated usability testing to ensure the voice of the user is heard during the design process.
• Tree testing: Also known as a reverse card sort, tree testing is used to evaluate the findability of information on a website. This method allows you to work backwards through your information architecture and test that thinking against real world scenarios with users.
• First click testing: Research has found that 87% of users who start out on the right path from the very first click will be able to successfully complete their task while less than half ( 46%) who start down the wrong path will succeed. First click testing is used to evaluate how well a website is supporting users and also provides insights into design elements that are being noticed and those that are being ignored.
• Hallway testing: Hallway testing is a usability testing method used to gain insights from anyone nearby who is unfamiliar with your project. These might be your friends, family or the people who work in another department down the hall from you. Similar to guerilla testing but less ‘wild’. This method works best at picking up issues early in the design process before moving on to testing a more refined product with your intended audience.

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Online usability testing tool: Tree testing 🌲🌳🌿

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Tree testing is a remote usability testing tool that uses tree testing to help you discover exactly where your users are getting lost in the structure of your website. Treejack uses a simplified text-based version of your website structure removing distractions such as navigation and visual design allowing you to test the design from its most basic level.

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Like any other tree test, it uses task based scenarios and includes the opportunity to ask participants pre and post study questions that can be used to gain further insights. Tree testing is a useful tool for testing those five key usability principles mentioned earlier with powerful inbuilt features that do most of the heavy lifting for you. Tree testing records and presents the following for each task:

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• complete details of the pathways followed by each participant
• the time taken to complete each task
• first click data
• the directness of each result
• visibility on when and where participants skipped a task

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Participant paths data in our tree testing tool 🛣️

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The level of detail recorded on the pathways followed by your participants makes it easy for you to determine the ease of use, learnability, efficiency and impact of errors of your website. The time taken to complete each task and the directness of each result also provide insights in relation to those four principles and user satisfaction can be measured through the results to your pre and post survey questions.

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The first click data brings in the added benefits of first click testing and knowing when and where your participants gave up and moved on can help you identify any issues.Another thing tree testing does well is the way it brings all data for each task together into one comprehensive overview that tells you everything you need to know at a glance. Tree testing's task overview- all the key information in one placeIn addition to this, tree testing also generates comprehensive pathway maps called pietrees.

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Each junction in the pathway is a piechart showing a statistical breakdown of participant activity at that point in the site structure including details about: how many were on the right track, how many were following the incorrect path and how many turned around and went back. These beautiful diagrams tell the story of your usability testing and are useful for communicating the results to your stakeholders.

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Usability testing tips 🪄

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Here are seven practical usability testing tips to get you started:

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• Test early and often: Usability testing isn’t something that only happens at the end of the project. Start your testing as soon as possible and iterate your design based on findings. There are so many different ways to test an idea with users and you have the flexibility to scale it back to suit your needs.
• Try testing with paper prototypes: Just like there are many usability testing methods, there are also several ways to present your designs to your participant during testing. Fully functioning high fidelity prototypes are amazing but they’re not always feasible (especially if you followed the previous tip of test early and often). Paper prototypes work well for usability testing because your participant can draw on them and their own ideas- they’re also more likely to feel comfortable providing feedback on work that is less resolved! You could also use paper prototypes to form the basis for collaborative design sessions with your users by showing them your idea and asking them to redesign or design the next page/screen.
• Run a benchmarking round of testing: Test the current state of the design to understand how your users feel about it. This is especially useful if you are planning to redesign an existing product or service and will save you time in the problem identification stages.
• Bring stakeholders and clients into the testing process: Hearing how a product or service is performing direct from a user can be quite a powerful experience for a stakeholder or client. If you are running your usability testing in a lab with an observation room, invite them to attend as observers and also include them in your post session debriefs. They’ll gain feedback straight from the source and you’ll gain an extra pair of eyes and ears in the observation room. If you’re not using a lab or doing a different type of testing, try to find ways to include them as observers in some way. Also, don’t forget to remind them that as observers they will need to stay silent for the entire session beyond introducing themselves so as not to influence the participant - unless you’ve allocated time for questions.
• Make the most of available resources: Given all the usability testing options out there, there’s really no excuse for not testing a design with users. Whether it’s time, money, human resources or all of the above making it difficult for you, there’s always something you can do. Think creatively about ways to engage users in the process and consider combining elements of different methods or scaling down to something like hallway testing or guerilla testing. It is far better to have a less than perfect testing method than to not test at all.
• Never analyse your findings alone: Always analyse your usability testing results as a team or with at least one other person. Making sense of the results can be quite a big task and it is easy to miss or forget key insights. Bring the team together and affinity diagram your observations and notes after each usability testing session to ensure everything is captured. You could also use Reframer to record your observations live during each session because it does most of the analysis work for you by surfacing common themes and patterns as they emerge. Your whole team can use it too saving you time.
• Engage your stakeholders by presenting your findings in creative ways: No one reads thirty page reports anymore. Help your stakeholders and clients feel engaged and included in the process by delivering the usability testing results in an easily digestible format that has a lasting impact. You might create an A4 size one page summary, or maybe an A0 size wall poster to tell everyone in the office the story of your usability testing or you could create a short video with snippets taken from your usability testing sessions (with participant permission of course) to communicate your findings. Remember you’re also providing an experience for your clients and stakeholders so make sure your results are as usable as what you just tested.

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Related reading 🎧💌📖

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• Usability testing with Optimal Workshop
• Usability Testing: Five types of usability tests
• Usability Heuristics: How to conduct a heuristic evaluation
• Interface Usability:User Interface Design Basics

For those new to the qualitative research space, there’s one question that’s usually pretty tough to figure out, and that’s the question of how many participants to include in a study. Regardless of whether it’s research as part of the discovery phase for a new product, or perhaps an in-depth canvas of the users of an existing service, researchers can often find it difficult to agree on the numbers. So is there an easy answer? Let’s find out.

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Here, we’ll look into the right number of participants for qualitative research studies. If you want to know about participants for quantitative research, read Nielsen Norman Group’s article.

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Getting the numbers right

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So you need to run a series of user interviews or usability tests and aren’t sure exactly how many people you should reach out to. It can be a tricky situation – especially for those without much experience. Do you test a small selection of 1 or 2 people to make the recruitment process easier? Or, do you go big and test with a series of 10 people over the course of a month? The answer lies somewhere in between.

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It’s often a good idea (for qualitative research methods like interviews and usability tests) to start with 5 participants and then scale up by a further 5 based on how complicated the subject matter is. You may also find it helpful to add additional participants if you’re new to user research or you’re working in a new area.

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What you’re actually looking for here is what’s known as saturation.

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Understanding saturation

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Whether it’s qualitative research as part of a master’s thesis or as research for a new online dating app, saturation is the best metric you can use to identify when you’ve hit the right number of participants.

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In a nutshell, saturation is when you’ve reached the point where adding further participants doesn’t give you any further insights. It’s true that you may still pick up on the occasional interesting detail, but all of your big revelations and learnings have come and gone. A good measure is to sit down after each session with a participant and analyze the number of new insights you’ve noted down.

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Interestingly, in a paper titled How Many Interviews Are Enough?, authors Greg Guest, Arwen Bunce and Laura Johnson noted that saturation usually occurs with around 12 participants in homogeneous groups (meaning people in the same role at an organization, for example). However, carrying out ethnographic research on a larger domain with a diverse set of participants will almost certainly require a larger sample.

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Ensuring you’ve hit the right number of participants

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How do you know when you’ve reached saturation point? You have to keep conducting interviews or usability tests until you’re no longer uncovering new insights or concepts.

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While this may seem to run counter to the idea of just gathering as much data from as many people as possible, there’s a strong case for focusing on a smaller group of participants. In The logic of small samples in interview-based, authors Mira Crouch and Heather McKenzie note that using fewer than 20 participants during a qualitative research study will result in better data. Why? With a smaller group, it’s easier for you (the researcher) to build strong close relationships with your participants, which in turn leads to more natural conversations and better data.

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There's also a school of thought that you should interview 5 or so people per persona. For example, if you're working in a company that has well-defined personas, you might want to use those as a basis for your study, and then you would interview 5 people based on each persona. This maybe worth considering or particularly important when you have a product that has very distinct user groups (e.g. students and staff, teachers and parents etc).

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How your domain affects sample size

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The scope of the topic you’re researching will change the amount of information you’ll need to gather before you’ve hit the saturation point. Your topic is also commonly referred to as the domain.

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If you’re working in quite a confined domain, for example, a single screen of a mobile app or a very specific scenario, you’ll likely find interviews with 5 participants to be perfectly fine. Moving into more complicated domains, like the entire checkout process for an online shopping app, will push up your sample size.

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As Mitchel Seaman notes: “Exploring a big issue like young peoples’ opinions about healthcare coverage, a broad emotional issue like postmarital sexuality, or a poorly-understood domain for your team like mobile device use in another country can drastically increase the number of interviews you’ll want to conduct.”

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In-person or remote

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Does the location of your participants change the number you need for qualitative user research? Well, not really – but there are other factors to consider.

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• Budget: If you choose to conduct remote interviews/usability tests, you’ll likely find you’ve got lower costs as you won’t need to travel to your participants or have them travel to you. This also affects…
• Participant access: Remote qualitative research can be a lifesaver when it comes to participant access. No longer are you confined to the people you have physical access to — instead you can reach out to anyone you’d like.
• Quality: On the other hand, remote research does have its downsides. For one, you’ll likely find you’re not able to build the same kinds of relationships over the internet or phone as those in person, which in turn means you never quite get the same level of insights.

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Is there value in outsourcing recruitment?

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Recruitment is understandably an intensive logistical exercise with many moving parts. If you’ve ever had to recruit people for a study before, you’ll understand the need for long lead times (to ensure you have enough participants for the project) and the countless long email chains as you discuss suitable times.

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Outsourcing your participant recruitment is just one way to lighten the logistical load during your research. Instead of having to go out and look for participants, you have them essentially delivered to you in the right number and with the right attributes.

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We’ve got one such service at Optimal Workshop, which means it’s the perfect accompaniment if you’re also using our platform of UX tools. Read more about that here.

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Wrap-up

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So that’s really most of what there is to know about participant recruitment in a qualitative research context. As we said at the start, while it can appear quite tricky to figure out exactly how many people you need to recruit, it’s actually not all that difficult in reality.

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Overall, the number of participants you need for your qualitative research can depend on your project among other factors. It’s important to keep saturation in mind, as well as the locale of participants. You also need to get the most you can out of what’s available to you. Remember: Some research is better than none!

At Optimal Workshop, we've always prided ourselves on being pioneers in the field of UX research tools. Since our inception, we've been the go-to platform for UX researchers and designers looking to conduct card sorting, tree testing, and other critical user research activities. Our tools have helped shape the digital experiences of some of the world's leading companies.

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The digital landscape is ever-changing, and with it, the needs of the professionals who create and optimize digital experiences. As we've grown and evolved alongside the industry, we've recognized the need to expand our reach and refine our value proposition to better serve not just UX researchers, but all professionals involved in delivering exceptional digital experiences.

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That's why we're excited to announce a significant brand refresh and value pivot for Optimal Workshop. This evolution isn't just about a new coat of paint – it's a fundamental shift in how we position ourselves and the value we provide to our users and the broader digital experience community.

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Why fix it if it ain’t broke? 💔🔨

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Expanding Our User Base

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While we've built a strong reputation among UX researchers, we've recognized that there's a broader audience of professionals who benefit from our tools and expertise. Product managers, marketers, customer experience specialists, and others involved in shaping digital experiences often lack access to professional-grade user research tools or the knowledge to effectively implement them.

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Our brand refresh aims to make Optimal Workshop more accessible and relevant to this wider circle of professionals, without losing the deep respect we've earned from UX experts.

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Adapting to market changes

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The UX research landscape has evolved significantly since we first entered the market. With the proliferation of prototyping tools and the increasing speed of digital product development, there's been a shift away from extensive upfront research. However, we firmly believe that incorporating the voice of the customer throughout the development process is more critical than ever.

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Our pivot allows us to emphasize the importance of integrating user research and insights at various stages of the digital experience lifecycle, not just during initial design phases.

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Leveraging our expertise

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As pioneers in the field, we have accumulated a wealth of knowledge about best practices in UX research and digital experience optimization. Our brand refresh positions us not just as a tool provider, but as a trusted partner and thought leader in the industry. We're doubling down on our commitment to sharing knowledge, standardizing best practices, and elevating the work of exceptional practitioners in the field.

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Meeting evolving business needs through effective UX

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The UX industry is evolving rapidly, with increasing investment and a diverse range of roles getting involved. From junior designers leveraging AI to seasoned researchers with deep expertise, the landscape is rich with talent and tools. However, the true value lies in how effectively these resources translate into business outcomes.

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Optimal Workshop recognizes that exceptional digital experiences are no longer just nice-to-have – they're critical for engagement, conversion, and overall business success. Our tools bridge the gap between UX insights and tangible ROI by:

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• Democratizing research: Enabling teams across experience levels to gather valuable user data quickly and efficiently.
• Accelerating decision-making: Providing fast, actionable insights that reduce design iterations and time-to-market.
• Enhancing team effectiveness: Facilitating collaboration and knowledge sharing between junior and senior team members.
• Driving business value: Directly linking UX improvements to key performance indicators and bottom-line results.

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In a landscape where basic UX practices are becoming table stakes, Optimal Workshop empowers organizations to go beyond the basics. We help teams leverage the full spectrum of UX expertise – from AI-assisted analysis to seasoned human insight – to create digital experiences that truly set businesses apart and deliver measurable returns on UX investment.

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What's changing at Optimal Workshop 🐛🦋

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1. Best-in-class research & insights platform

While our core tools remain a critical part of our offering, we're broadening our focus to position Optimal Workshop as a best-in-class research & insights platform for digital experience professionals. This means developing new tools, workflows, and integrations that cater to a wider range of use cases and user types.

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2. Accessibility without compromise

We're committed to making our professional-grade tools more accessible to a broader audience without sacrificing the depth and rigor that our expert users expect. This means developing new onboarding experiences, creating more intuitive interfaces, and providing educational resources to help users at all levels get the most out of our platform.

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3. Championing best practices

As part of our evolution, we're placing a greater emphasis on identifying, sharing, and standardizing best practices in digital experience research and optimization. Through case studies, partnerships with industry leaders, and our own thought leadership content, we aim to elevate the entire field of digital experience design.

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4. Fostering a community of excellence

We're doubling down on our commitment to building and nurturing a community of digital experience professionals. This includes expanding our educational offerings, hosting more events and webinars, and creating opportunities for our users to connect and learn from each other. 

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5. Emphasizing outcomes and ROI

We're aligning our messaging and product development with the real-world impact our users are seeking. That’s why the new names for our tools emphasize what each tool helps you achieve, rather than the technical methodology behind it. This outcome-focused approach helps users quickly identify which tool is right for their specific needs.

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How our evolution benefits you 🚀

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For our long-time users, rest assured that the tools and features you know and love aren't going anywhere, but their names are changing to plain English terms to be more approachable for professionals who may not have a background in UX research. In fact, our UXR platform is only going to get better as we invest in improvements and new capabilities. You'll also benefit from an expanded community of practitioners and a wealth of new resources to help you continue to grow and excel in your field.

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For professionals who may be new to Optimal Workshop or to formalized user research in general, our refresh means it's easier than ever to get started with professional-grade tools and methodologies. We're here to support you at every step, from your first card sort to building a comprehensive, data-driven approach to optimizing digital experiences.

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Join us in shaping tomorrow's digital experiences 🌟

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This brand refresh and value pivot mark an exciting new chapter for Optimal Workshop. We're committed to continuing our tradition of excellence while expanding our reach and impact in the world of digital experiences.

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As we move forward, we'll be rolling out new features, resources, and initiatives that align with our refreshed brand and value proposition. We're excited to partner with our users – both new and long-standing – to push the boundaries of what's possible in creating truly exceptional digital experiences.

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Thank you for being part of the Optimal Workshop community. Whether you're a UX research veteran or just starting your journey in optimizing digital experiences, we're here to support you with the best tools, knowledge, and community in the industry. Together, we can shape the future of digital experiences and make the online world more intuitive, efficient, and enjoyable for everyone.

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Onwards and upwards,

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Alex Burke, CEO Optimal Workshop

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