Koji vs Userbrain: AI Interviews vs Unmoderated User Testing (2026)

TL;DR: Userbrain is an unmoderated user testing platform where participants record think-aloud sessions on your website, app, or prototype, with optional access to a 170k+ tester panel. Koji is an AI-native customer research platform that runs moderated voice and chat interviews and automatically generates thematic analysis. Both are "remote research," but they answer fundamentally different questions: Userbrain tells you whether a specific UI works, Koji tells you what your customers actually need. Userbrain Starter is €99/month (annual billing, +20% for monthly); Koji Insights is €29/month with a free tier to start.

Quick answer: which tool do you actually need?

• Choose Userbrain if your core problem is usability of a specific interface — you have a site, app, or prototype and you need to watch strangers attempt tasks and tell you what is confusing.
• Choose Koji if your core problem is understanding customers — discovery, churn, value prop, win/loss, PMF, JTBD, brand perception, or anything that needs a real conversation with structured questions and follow-up probes.

If you run both, it is typically Userbrain for one-off usability passes on a new flow, and Koji as the always-on research engine for everything else.

What is Userbrain?

Userbrain is an unmoderated remote user testing tool founded in Austria in 2014. Customers upload a website, app, or prototype, write task instructions, and either invite their own users or recruit from Userbrain's panel of 170k+ testers. Testers record a 5–20 minute think-aloud session — their screen, their voice, and their face if enabled — and submit the video for review.

Userbrain's strengths:

• Cheap, fast unmoderated tests with results in 24 hours when using the panel
• Free testers from your own users with the right plan (100 sessions/month included on Starter)
• AI assistant that highlights notable moments in test recordings to speed up analysis
• Works on web, iOS, Android, and prototypes (Figma supported)

Common complaints from public review sites (Capterra, G2, Userbrain's own blog): testers can be inconsistent, with some users rushing through tasks; no tree testing, no session recording in advanced mode, no moderated mode; and a subscription model that confuses some teams.

What is Koji?

Koji is an AI-native customer research platform that runs moderated interviews with respondents over voice or chat. A researcher defines a study brief, customizes the AI consultant, and shares a link — respondents complete a 5–30 minute interview where the AI moderator asks structured questions, probes for depth, and adapts dynamically. After the conversation, Koji automatically produces thematic analysis, identifies frequent themes with verbatim quotes, and publishes a one-click report.

Koji ships with:

• AI-moderated voice or chat interviews with dynamic follow-ups
• Six structured question types in a single study: open-ended, scale, single choice, multiple choice, ranking, yes/no
• Automatic AI thematic analysis — no manual tagging
• Customizable AI consultants per study
• One-click published reports
• Quality gate — only conversations scoring 3+ consume credits so spam does not burn budget

For a deeper dive into the methodology, see our docs on AI-moderated interviews and moderated vs unmoderated research.

The core difference: tasks vs conversations

The biggest mental shift between these two tools:

• Userbrain optimizes for tasks. You ask testers to "find the pricing page" or "complete checkout." You get a video of someone trying. Output: usability issues on a specific interface.
• Koji optimizes for conversation. You ask respondents to "tell me about the last time you tried to solve this problem" or "what would have made you stay?" You get a moderated interview with thematic analysis. Output: an understanding of customer motivation.

Both are valuable. They are not interchangeable. The 2025 Greenbook GRIT report shows 72% of insights teams now use AI in qualitative research, up from 31% two years prior — the shift is toward conversation, not just task observation.

Feature-by-feature comparison

| Capability | Userbrain | Koji | |---|---|---| | Unmoderated task recordings | Yes — core feature | No | | AI-moderated voice interviews | No | Yes | | AI-moderated chat interviews | No | Yes | | Dynamic follow-up probes | No | Yes | | Automatic thematic analysis | Highlights only | Full thematic clustering with quotes | | Six structured question types | Survey-style only | Yes (in one study) | | Customizable AI moderator | No | Yes | | Built-in 170k tester panel | Yes | No (bring your own users) | | Free tier | No (trial only) | Yes | | Entry price | €99/mo (annual) | €29/mo Insights | | Cost per panel tester | $45 per session | N/A (BYO users) | | Quality gate on responses | Manual rating | Automatic 3+ scoring gate | | Best for | Usability testing | Discovery, churn, win/loss, PMF, JTBD |

Pricing in 2026

Userbrain (annual billing):

• Starter — €99/month (€1,188/year), includes 100 sessions/month with your own users
• Pro — €299/month (€3,588/year)
• Agency — €799/month (€9,588/year)
• Monthly billing costs 20% more
• Panel testers — $45 per session, incentives included

Koji (2026):

• Free — one-time signup credit grant
• Insights — €29/month or €290/year (29 credits)
• Interviews — €79/month or €790/year (79 credits)
• Overage — €1/credit flat
• Only conversations scoring 3+ consume a credit

For a team running 20 customer interviews a month with their own users, Koji costs €29/month and produces thematic analysis automatically. Userbrain at the same volume of panel sessions ($45 × 20 = $900) costs over 30x more — and what you get is video, not analysis. If you bring your own users to Userbrain Starter, you pay €99 and still do the analysis yourself.

Where Userbrain wins

Userbrain is genuinely useful for one job: cheap, fast unmoderated usability testing. Specifically:

• You have a prototype and need fresh eyes — the 170k panel delivers fresh testers in 24 hours
• You are testing a specific flow — checkout, onboarding, signup — and you want to watch strangers try it
• You do not care about the conversation — you just want to see where people get stuck
• You need video evidence — recordings are great for showing stakeholders exactly where a UI breaks

If your research workflow is "ship a flow, watch 5 strangers use it, fix the issues," Userbrain is built for that. See our usability testing guide for the broader methodology.

Where Koji wins

Koji wins anywhere the question is why instead of can they do this task. Some examples:

• Customer discovery — running pre-product interviews to understand what users need. See our customer discovery interview guide.
• Churn analysis — finding the real reasons customers leave, not the polite ones in cancellation forms. Industry data shows the stated reason is wrong about 40% of the time.
• Win/loss interviews — understanding why deals went one way or the other.
• Value proposition testing — probing whether a positioning resonates and why.
• PMF and JTBD research — extracting the underlying job a customer is hiring your product to do.
• Continuous discovery — weekly customer conversations so you never lose touch. See continuous discovery tools 2026.

In all of these, you need an interview that probes follow-ups dynamically — exactly what AI moderation provides. Industry benchmarks show AI-moderated interviews generate 4.5x more insightful responses than traditional surveys.

On the tester quality problem

A real concern in the Userbrain review corpus: tester quality on the panel can be inconsistent. Users have reported testers rushing tasks, giving low-effort feedback, or not matching screener criteria. This is structural to any large panel — quality varies, even with screening.

Koji takes a different approach. Because Koji is moderator-first, the AI moderator drives the conversation forward and probes for depth. If a respondent's answer is shallow, the moderator asks again — and again. Koji's quality gate also automatically filters submissions: only conversations scoring 3+ on internal quality consume a credit. That is structurally impossible in a recorded-video model where you pay per submission regardless of effort.

Pricing math for a typical product team

Scenario: 20 interviews per month, your own users.

• Userbrain panel — $45 × 20 = $900/month, plus video review and manual analysis time
• Userbrain Starter (own users) — €99/month (100 sessions included), but you watch 20 videos and synthesize manually
• Koji Insights — €29/month (29 credits), with automatic thematic analysis and one-click reports

If you have your own users, Userbrain Starter is competitive on raw price. The hidden cost is what happens after the recording — you still watch 20 videos, take notes, and synthesize. Koji ships the synthesis with the platform. Most teams that move to Koji report cutting analysis time by 60–80% on the same volume of conversations.

Statistics that matter in 2026

• 72% of insights teams use AI in qualitative research in 2025, up from 31% two years prior (Greenbook GRIT 2025).
• 4.5x more insightful responses on AI-moderated interviews vs traditional surveys.
• 40% — share of customer churn reasons that are misattributed in stated-reason exit data, per industry studies.
• 170k+ testers in the Userbrain panel — large, but quality variance is the most cited complaint on review sites.
• $45 per Userbrain panel tester vs roughly €1 per credit on Koji overage — a 50x difference at unit cost.

When most teams use both

Reasonable workflow:

1. Discovery (Koji) — what are users trying to accomplish? What language do they use?
2. Build the flow.
3. Usability check (Userbrain) — watch 5–10 strangers attempt the flow.
4. Iterate.
5. Post-launch research (Koji) — what is working? Why are some users churning? What do they want next?

Userbrain fills the usability slot. Koji fills everything before and after. For most product, growth, CX, and research teams, Koji is the higher-leverage tool simply because the volume of qualitative research dwarfs the volume of unmoderated usability checks.

Common alternatives to Userbrain

If you are evaluating Userbrain alongside other unmoderated testing tools, also look at:

• UserTesting — much larger panel, enterprise pricing (see our Koji vs UserTesting 2026 comparison)
• Maze — broader UX research platform (see Koji vs Maze 2026)
• Lyssna (formerly UsabilityHub) — surveys and quick design tests (see Koji vs Lyssna 2026)
• TryMyUI / Trymata — competing unmoderated panel

For deep qualitative depth — the part that none of these tools really cover — Koji is the AI-native answer.

The bottom line

Userbrain is solid at one thing: low-cost unmoderated usability testing. Koji is built for everything else — discovery, churn, value prop, win/loss, PMF, continuous insight. It runs AI-moderated voice and chat interviews, six structured question types, automatic thematic analysis, and one-click reports at €29/month with a free tier.

Ready to see what AI-moderated interviews look like in your hands? Start your free Koji trial and run your first study today.