We make the invisible visible.

Replay started with a simple belief: if you can't see what your software is doing, you can't fix it. We built the technology to change that — for developers, for AI agents, and for anyone building with code.

Where we started

Debugging has always been the same: guess what went wrong, try a fix, see if it works. Repeat until you get lucky or give up and rewrite.

We thought that was broken. Our founders spent a decade at Mozilla working on the Firefox browser engine — one of the most complex software systems ever built. They saw firsthand how much time gets lost to bugs that nobody can reproduce, errors that nobody can explain, and fixes that nobody is confident about.

So they built Replay: a way to record exactly what your software did and play it back, step by step. Not a video. Not a log file. A deterministic capture of every DOM change, network request, and state update — the full picture, down to the last detail.

In the early days, we gave developers a superpower: the ability to time travel through their recordings. Step forward, step back, inspect state at any point in time. No reproduction required. No guessing. Just the truth.

Where we're going

Today, the way software gets built has fundamentally changed. AI agents write code, spin up apps, and iterate faster than any human team could. But speed without visibility creates a new problem: apps ship with bugs nobody caught, because nobody was watching.

That's the gap Replay QA was built to close. Replay QA autonomously explores your app, records every session, and surfaces real bugs with root causes and suggested fixes — before your users find them.

We've built Replay QA to work alongside your coding agent. Drop in a URL for on-demand testing, or connect a GitHub repo for a continuous quality gate that runs every time you ship. Either way, bugs are caught, analyzed, and handed back to your agent to fix — automatically.

We're building toward a world where shipping broken software is the exception, not the rule — where every app gets tested, every bug gets caught, and no user ever hits a problem that could have been found first.

How we work

The principles behind the product.

Clarity over cleverness

We build tools that show you exactly what happened — no abstractions, no hand-waving. That same principle runs through everything we do: our code, our communication, and our product.

Long-term over fast

We're not optimizing for the next quarter. We're building technology that changes how software gets built and debugged. That takes patience, and we're built for it.

Open over closed

We're a distributed team across time zones and continents. We care about what you ship, not when you're online. And we believe the tools that make software understandable should be accessible to everyone — not just engineers at big companies.

The team

Founded by ex-Mozilla engineers. Distributed globally. Building the future of debugging.

Brian Hackett
CEO
Stanford Ph.D. with 10 years at Mozilla, where he worked on the systems that power the Firefox browser engine. Brian started Replay to solve the problem he spent a decade fighting: helping developers understand complex systems when things go wrong. When he's not building Replay, he's sailing or traveling in a van.
Mark Erikson
Software Engineer
The maintainer of Redux and creator of Redux Toolkit — tools used by millions of React developers worldwide. Mark brings deep expertise in developer tooling and an obsessive focus on developer experience. Based in Southwest Ohio.
Dominik Seifert
Software Engineer
Two decades of software engineering, from MMORPG servers to CUDA optimization. Dominik holds a Ph.D. in systems analysis and brings the kind of low-level systems knowledge that makes Replay's recording engine possible. Based in Taiwan, originally from Germany.
Thomas Daly
Head of Product
Thomas is a product builder/maker that lives at the intersection of the customer and the product, while reading the tea leaves of the shifting landscape. Obsessed with the details of making great things, and loves nothing more than to do with good people. He talks about hospitality vs. hostility a lot. He lives in the lower Hudson River valley in NY.
Strider Wilson
Software Engineer
Frontend Software Engineer focused on building clean, intuitive user experiences that make complex technology feel simple. Strider specializes in React, TypeScript, and modern UI architecture, turning ambitious ideas into polished, scalable products. With experience across startups, product design, and fast-moving engineering teams, he enjoys solving hard problems through thoughtful design and efficient code. Outside of tech, he brings an adventurous mindset shaped by years as a wingsuit BASE jumper, skydiving instructor, photographer, and creator.

The code behind our code: Integrity, honesty, and decency. Our principles are not aspirations but constraints. They lie behind every action we take, or decision we make. They ensure that we remain true to our course and true to ourselves.
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Embedded values: Our values anchor our aspirations and drive us forward.
We are making software development faster, more accessible, more inclusive, and more exciting. We are dedicated to building a world where everyone is technically literate, a world where we are better equipped to overcome the greatest of challenges.
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Test your app for free.

Give Replay QA a URL. No test suite, no QA team, no credit card required.