Replay captures the full browser runtime — every DOM change, network request, and state update — and turns it into a root cause and a specific fix. No manual debugging.
Trusted by top engineering teams
A test fails. A user hits a bug. Your agent takes a guess at the fix, pushes it, and the same test fails again. Without runtime context, agents are stuck in a loop — guessing, patching, retrying.
The problem isn't the agent. It's that the agent has no way to see what actually happened in the browser. No DOM state, no network timing, no component re-renders. It's debugging blind.
You end up pulling the agent aside, opening DevTools yourself, and spending an hour doing the work manually. The whole point of the agent was to save you that time.
That's why we built Replay
Replay captures a deterministic recording — every DOM change, network request, JS execution frame, and state update. Using Replay MCP, your coding agent can analyze the recording, trace the exact causal chain from failure to root cause, and deliver the root cause and a suggested fix. No guessing. No manual debugging. No human required.
You might be thinking “how is this different than the monitoring tools I'm already using?” We made this video for you.
Replay's time-travel debugging works wherever your tests run and wherever your agent works. Most teams use all three.
In your CI pipeline
The Replay CI Agent installs as a GitHub bot. It records every Playwright run on every PR. When a test fails, Replay analyzes the recording and posts root cause plus a suggested fix as a PR comment — automatically.
Set up the CI Agent →In your IDE
Replay MCP connects to Cursor, Claude Code, Codex, Copilot, or Windsurf in one command. Your coding agent can step through any recorded execution, inspect state at any point in time, and identify root causes — right inside your IDE.
Set up Replay MCP →In your browser
The Replay Chrome extension lets engineers and QA capture a deterministic recording of any bug — on localhost, a staging environment, or production. Record it once, hand it to your agent or step through it yourself. No reproduction required.
Install the extension →See how Replay MCP lets your agent dive in and explain the problem.
Creating a new task does nothing
The form to add a new task isn't doing anything
I'll investigate why the form to add a new task isn't working. Let me start by exploring the recording to understand what's happening.
Let me look at the CreateTaskModal component more closely to understand its implementation, especially the form submission logic.
I can see the form submission logic. Line 53-54 shows handleSubmit was called once, but let me check where the onSave callback leads to. Let me look at TasksListPage to see how the modal's onSave is handled.
I found the issue! Looking at handleCreateTask (lines 73-93):
setCreateModalOpen(false) (hit count: 1)fetch call to actually save the task!The function closes the modal at the end, but it never makes a network request to persist the new task. The payload is built but never sent to the server.
The handleCreateTask function in TasksListPage.tsx is missing the API call to create the task. It:
fetch to POST the task to the backend ✗Compare this to line 65-70 where fetch is used to load deals - a similar pattern should exist after building the payload on line 92, but it's missing. The function just closes the modal without actually saving anything.
Three things Replay delivers on every bug.
Replay doesn't just report the error. It traces through the recording to find the exact cause — the state change, the failed request, the bad render — and explains why it happened.
Your agent receives a specific, implementation-ready fix with full context — which file, which function, what to change, and why. No more trial-and-error loops.
Replay MCP connects to Claude Code, Codex, Cursor, Copilot, Windsurf, and any agent that supports MCP. Add it once and every agent in your workflow gets full runtime visibility.
Claude Code
Codex
Cursor
Copilot
WindsurfCase Studies
“Before Replay We spent somewhere between 1–2 hours per day per dev in this reproducibility purgatory. The toll this was taking on our development velocity and our ability to respond and resolve issues was huge. We thought there must be a better way.”
Read full case study
Mark Probst
@VP Eng, Glide
“If I didn’t have Replay, it would have taken me several days or even weeks getting the debugger to run properly in all the dynamically loaded scripts, which is not easy. With Replay it took me half a day to figure it out and get a fix ready.”
Read full case study
Simeon Cheeseman
@Tablecheck, Principal Engineer
“The tools that we were using before were barely better than useless. You’d say thanks for the console log screenshot and spend 2–3 days trying to recreate the issues and finding it in the code. With Replay, all that wasted time has been eliminated.”
Read full case study
Shane Duff
@Pantheon, Front End Lead
Testimonials
“Next.js App Router is now stable in 13.4. Wouldn’t have been possible without Replay, we investigated so many (over 20) super complicated bugs that using traditional debugging would have cost us days to investigate.”
Tim Neutkins
@Co-author of Next.js
“I think Replay has a very good chance of creating a new category around collaborative debugging”
Guillermo Rauch
@Founder of Vercel
“When I see a hard-to-reproduce issue in GitHub, I ask for a replay.”
JJ Kasper
@Co-author of Next.js
“If I don't immediately know the answer to a bug, I immediately reach for Replay.io. It's like HMR for repros.”
Sebastian Markbåge
@React Maintainer
“Replay.io is galaxy brain tooling. Real gamechanger.”
Dan Abramov
@React Maintainer
“I think Replay has a very good chance of creating a new category around collaborative debugging”
Guillermo Rauch
@Founder of Vercel
“When I see a hard-to-reproduce issue in GitHub, I ask for a replay.”
JJ Kasper
@Co-author of Next.js
“If I don't immediately know the answer to a bug, I immediately reach for Replay.io. It's like HMR for repros.”
Sebastian Markbåge
@React Maintainer
“Replay.io is galaxy brain tooling. Real gamechanger.”
Dan Abramov
@React Maintainer
“Programmers typically reach for debuggers when they run out of ideas on how to fix their code. Now coders reach for time-travel debugging to understand their programs and not just when they want to fix a bug.”
Amjad Masad
@Founder Replit
“Fast forwarding and rewinding to breakpoints has saved me days(weeks??) while hunting down issues in @solid_js interruptible concurrent rendering.”
Ryan Carniato
@Solid Founder
“Replay.io gives me the tools I need to solve seemingly impossible bugs. It’s like the Redux DevTools, but for every line of code in your app.”
Mark Erikson
@Redux Maintainer
“Replay.io allows me to debug problems that would be impossible to debug by traditional means - it has saved me from countless hours of confusion and frustration.”
Lenz Weber-Tronic
@Redux Toolkit Maintainer
“I’m not sure if we could’ve shipped the last major version of RedwoodJS without Replay.”
Dom Saadi
@Maintainer of RedwoodJS
“Replay.io is so great! Today I had a hard-to-repro flow in development, so I recorded a replay to see how it works. I didn’t only find the bug, I discovered a performance improvement using Replay.”
Ives van Hoorne
@Co-founder CodeSandbox
“Current status: time-travel debugging Typescript's compiler. Replay is the hero tool I don't deserve. My dev life consists of 2 major eras now - I call them pre-Replay and post-Replay.”
Mateusz Burzyński
@OSS Contributor to Typescript
“Replay.io is from another planet where bug reports save you time, instead of eating up hours of debugging.”
Matt Pockock
@Full-time TypeScript educator
“Time travel is the obvious next step for the future of collaboratively inspecting and debugging applications.”
David Khourshid
@Founder of Stately.ai
“People use the word "game-changer" waaaaay too often. Very rarely does anything change the game. But this just might! I'm sharing it to all of my teams.”
Erik Rasmussen
@Author of Redux form and final form
“Replay.io is one of these experiences that first feels like magic – but after squashing your first bugs with it, you will quickly wonder how you ever worked without it”
Harald Kirschner
@Product Manager, VS Code
“Replay.io is the most significant leap forward for debugging since we introduced the step debugger”
Kenneth Auchenberg
@Developer Products, Stripe
“If a picture is worth a thousand words, a replay is worth a thousand pictures”
Zack Rosen
@CEO of Pantheon
“Recording and debugging flaky tests with Replay.io feels like hopping in Doc Brown’s DeLorean and flying back to the time of the crash!”
Gleb Bahmutov
@Distinguished Engineer, Cypress
“Before Replay.io, we spent somewhere between 1–2 hours per day per dev in this reproducibility purgatory”
Mark Probst
@Glide apps, VP Eng
Wherever your agent gets stuck on a bug it can't see, Replay closes the gap.
Your coding agent hits a failing test or runtime error. Instead of looping, it sends the recording to Replay and gets a precise fix back — then implements it.
Record every test run. When a test flakes, Replay analyzes the recording and delivers the root cause and fix to your agent — no manual investigation needed.
A user reports a bug. Replay captures the session, generates the diagnosis and fix. Your agent applies it. You review the PR.
When your agent loops on a problem — retrying the same patch, failing the same test — Replay gives it the runtime context it needs to break out.
Without Replay
With Replay
Free to get started. No credit card required.