Koji vs Optimal Workshop: AI Customer Interviews vs IA Testing (2026)

TL;DR: Optimal Workshop is an information-architecture-first UX research platform built around card sorting, tree testing, first-click testing, and surveys. Koji is an AI-native customer research platform built around moderated voice and chat interviews that automatically produce thematic analysis. They sit at opposite ends of the UX research workflow — Optimal Workshop helps you organize a site or product's structure, Koji helps you understand why users behave the way they do. Optimal Workshop starts at $199/month with a 5-study annual cap; Koji's Insights plan starts at €29/month with unlimited studies and 29 conversation credits included.

Quick answer: which tool do you actually need?

• Choose Optimal Workshop if your core problem is information architecture — you need to test menu labels, validate a navigation structure, run an open or closed card sort, or measure findability on a prototype.
• Choose Koji if your core problem is qualitative research depth — discovery interviews, churn deep-dives, value-proposition testing, win/loss analysis, or any study where you need a real conversation and a thematic analysis at the end.

Most product teams need both at different stages: Optimal Workshop while restructuring a site, Koji throughout the rest of the year.

What is Optimal Workshop?

Optimal Workshop is a UX research suite focused on information architecture and usability. Its flagship tools are:

• OptimalSort — open, closed, and hybrid card sorting
• Treejack — tree testing for site navigation
• Chalkmark — first-click testing on prototypes and designs
• Reframer — qualitative observation notes (closer to a notes app than an interview platform)
• Questions — surveys

Optimal Workshop launched in 2008 and has been the default IA testing tool at large enterprises for over a decade. The platform shines when you have an existing site or prototype and you need to validate whether users can find things.

It is not a customer interview platform. There is no AI moderator, no automatic thematic analysis on open-ended responses, and no voice. Reframer captures observation notes during sessions you run elsewhere — it does not run the session.

What is Koji?

Koji is an AI-native customer research platform built around moderated interviews. Researchers write a study brief, customize an AI consultant for that study, and share a link — respondents complete a 5–30 minute voice or chat interview, the AI moderator asks structured questions and dynamic follow-ups, and Koji auto-generates thematic analysis and a published report.

The pillars:

• AI-moderated voice or chat interviews with dynamic follow-up probes that go beyond a single answer
• Six structured question types: open-ended, scale, single choice, multiple choice, ranking, yes/no — so you can mix qualitative depth with quant signal in the same study
• Automatic AI thematic analysis that clusters responses into themes with quotes and frequency
• Customizable AI consultants so the moderator matches your study (founder, researcher, UX lead, B2B specialist)
• One-click reports that turn raw conversations into shareable findings

Koji is a research depth tool. It is not designed to replace card sorting or tree testing.

Feature-by-feature comparison

| Capability | Optimal Workshop | Koji | |---|---|---| | Card sorting (open/closed/hybrid) | Yes — best in class | No | | Tree testing (Treejack) | Yes — best in class | No | | First-click testing (Chalkmark) | Yes | No | | AI-moderated voice interviews | No | Yes | | AI-moderated chat interviews | No | Yes | | Dynamic follow-up probes | No | Yes | | Automatic AI thematic analysis | No (manual tagging in Reframer) | Yes | | Structured question types | Surveys only | 6 types in one study | | One-click published reports | Manual | Yes | | Number of studies | 5/year on Starter | Unlimited | | Entry price | $199/mo (Starter) | €29/mo (Insights) | | Free tier | No (trial only) | Yes |

Pricing breakdown

Optimal Workshop (2026):

• Starter — $199/month, capped at 5 studies launched per year
• Enterprise — custom pricing with workspaces, admin controls, and a CSM
• All plans include unlimited seats and unlimited participants per study

Koji (2026):

• Free — one-time credit grant, no recurring credits
• Insights — €29/month or €290/year (29 credits/month)
• Interviews — €79/month or €790/year (79 credits/month)
• Overage — flat €1/credit
• Quality gate: only conversations scoring 3+ consume credits (so junk submissions do not burn your budget)

At Insights pricing, you can run roughly 29 interviews per month before overage — for the cost of one month of Optimal Workshop Starter, you get six months of Koji.

Where Optimal Workshop wins

If your core deliverable is a sitemap, a navigation, or a content taxonomy, Optimal Workshop is genuinely best-in-class. Its IA tools have been refined over 15+ years and are deeply trusted by enterprise UX teams. Specifically:

• Statistical rigor on IA tests — confidence intervals on first-click and findability scores
• OptimalSort dendrograms that visualize how participants grouped concepts
• Treejack click-by-click pathways for diagnosing where users get lost in your menu

If you only run IA studies and never need to understand why customers churn, why they hesitate to buy, or what their job-to-be-done is — Optimal Workshop is enough. For a deeper dive into when these methods make sense, see our card sorting guide and tree testing guide.

Where Koji wins

Koji wins anywhere a single closed-ended response or a click pattern is not enough. The 2025 Greenbook GRIT report shows 72% of insights teams now use AI in qualitative research, up from 31% two years prior — and the reason is depth at scale.

Specific advantages:

• The "why" question — Optimal Workshop tells you that 60% of users could not find Settings. Koji tells you the language they used, the workarounds they tried, and the mental model they expected.
• Async voice at scale — respondents complete a Koji interview on their own time, in their own voice, anywhere in the world. No moderator scheduling.
• Automatic thematic analysis — instead of tagging 30 Reframer notes by hand, Koji clusters open-ended responses into themes with frequencies and verbatim quotes. See analyzing AI-moderated interview results.
• AI-moderated focus groups — for early-stage concept testing where you need group dynamics, Koji can run a parallel cohort of one-on-one AI interviews that produce focus-group-quality insight without the recruiting tax. (See our docs on AI-moderated focus groups.)
• Six question types in one study — open-ended, scale, single choice, multiple choice, ranking, yes/no. You get qualitative depth and quant signal in a single flow.
• Customizable AI consultant — different study, different moderator persona. A B2B win/loss interview asks different things than a consumer concept test.
• One-click reports — go from raw conversation to a shareable findings deck in minutes, not weeks.

When most teams use both

Realistically, a mature product or UX team uses both tools at different stages of the same project:

1. Discovery (Koji) — understand what users are trying to accomplish, what language they use, what jobs they are hiring your product to do. See our customer discovery interview guide.
2. IA design (Optimal Workshop) — translate that language into a structure, then test card sorts and tree tests to validate the structure with users.
3. Concept validation (Koji) — once you have a prototype, run an AI-moderated interview study to surface objections, motivations, and value-proposition feedback. See setting up voice interviews.
4. Continuous discovery (Koji) — keep weekly customer interviews running once you ship. See our guide on continuous discovery tools 2026.

Optimal Workshop sits inside step 2. Koji sits inside steps 1, 3, and 4. They are complements, not substitutes — until you look at the total spend and realize Koji at €29/month is doing the heavier lift for a fraction of the cost.

Statistics that matter in 2026

• 72% of insights teams use AI in qualitative research as of 2025 (Greenbook GRIT report) — up from 31% two years prior.
• 4.5x more insightful responses on AI-moderated interviews vs traditional surveys (industry benchmarks).
• $15,000–$30,000 per session for traditional in-person focus groups; AI-moderated equivalents can be run for under €50 in credits.
• Six weeks is the typical traditional research timeline — far slower than modern product teams shipping every two weeks.

Common alternatives to Optimal Workshop

If you are comparing Optimal Workshop against other tools, also look at:

• UXtweak — directly competitive on IA + usability
• Maze — broader UX research platform with usability testing (see our Koji vs Maze 2026 comparison)
• Useberry — prototype testing
• Lyssna (formerly UsabilityHub) — first-click and design surveys (see Koji vs Lyssna)

If your real need is qualitative depth at the front and back end of those studies, Koji is the modern AI-native option that replaces a whole tier of recruiting, moderation, and analysis work.

The bottom line

Optimal Workshop will always have a place in IA-heavy projects. But the heavy lifting — figuring out what customers want, why they churn, why they buy — has moved to AI-moderated platforms. Koji gives you AI-moderated voice and chat interviews, six structured question types, automatic thematic analysis, and one-click reports at €29/month with a free tier to start.

Ready to see what Koji can do? Start your free trial and run your first AI-moderated customer interview today.