Tadeus vs Strella (2026)
Tadeus and Strella both run AI-moderated interviews with dynamic follow-ups, but they serve different research questions. Strella is built for product and UX teams testing concepts and usability, with screen and video recording so you can watch users interact with a design. Tadeus is built for employees and workforce populations, voice only, with an API for embedding interviews in other platforms.
Quick answer: Choose Strella when you are testing products, concepts, or usability with customers and want to see their screen. Choose Tadeus when you are interviewing employees or a workforce population, need voice-only interviews with no emotion inference, or want to embed interviews inside your own product.
At a glance
| Tadeus | Strella | |
|---|---|---|
| Primary focus | Workforce and embedded interviews | Customer and UX research |
| Modality | Voice only | Voice, screen, video |
| Languages | 70+ | Multiple |
| Stimuli testing | No | Embedded stimuli with screen recording |
| Repository | Transcript plus structured JSON per interview | AI and human-moderated interviews in one repository |
| Emotion inference | None by design | Captures video signal |
| Embedding | REST API and webhooks | Web platform |
What Strella does best
Strella is a strong fit for product teams. Its AI moderator runs dynamic follow-ups, synthesises in real time, and produces instant highlight reels. Screen and video recording mean participants can react to embedded stimuli, prototypes, and live products while the researcher watches exactly what they saw. It also stores AI-moderated and human-moderated interviews in one repository, so a team’s qualitative work stays in one place.
If your questions are about how customers use and react to your product, Strella is built for that.
What Tadeus does best
Tadeus targets a population Strella does not: the workforce. An AI agent holds a spoken conversation in over 70 languages, probes and branches on answers, can verify identity or call external systems mid-conversation, and returns a transcript plus structured JSON. It is voice only, with no video and no emotion inference. It works from transcripts and retains no audio.
Against Strella, that matters in two places:
- Employees. The EU AI Act prohibits inferring emotion in the workplace from February 2025. Screen and video capture suit customer research, but workforce deployments need a tool that stays clear of emotion inference entirely. Tadeus was built for that constraint.
- Embedding. Tadeus ships a REST API with webhooks, so HCM platforms and workforce software can run interviews inside their own product. Strella is a destination research platform.
How to decide
- Concept and usability testing with customers: Strella. Screen recording and embedded stimuli are exactly what that work needs.
- A single repository for AI and human interviews: Strella.
- Employee or workforce research: Tadeus. Voice only and no emotion inference keeps you inside the EU AI Act line.
- Participants answering by phone, between shifts, or off-desk: Tadeus. Voice needs no screen or camera.
- You want interviews inside your own product: Tadeus, via the API and webhooks.
For the research case on voice-only interviews, see Why voice, not video. For the full market view, see The Best AI-Moderated Interview Tools (2026).
Frequently asked questions
Is Tadeus or Strella better for employee research?
Tadeus. It is voice only, retains no audio, and does not infer emotion, which is the main EU AI Act concern when interviewing employees. Strella is built for customer and UX research.
Is Tadeus or Strella better for usability testing?
Strella. Usability work benefits from watching the participant’s screen while they talk, and Strella records screen and video with embedded stimuli. Tadeus has no screen capture.
Can either tool be embedded in another product?
Tadeus is designed for embedding, with a REST API and webhooks so interviews run inside your own software. Strella is used through its own platform.
Last updated July 2026. Tadeus publishes this comparison. The Strella summary is based on its public product pages and is kept factual so the page is useful whichever tool you choose.