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Dev tools · September 15, 2021

Time travel debugger for web development

Automated Penetration Testing for AI-Built Apps

Time travel debugger for web development launched on September 15, 2021 with 681 votes, #9 of 2,941 launches that month and more than 99% of that year's launches. The site was still online in September 2026, 5 years on.

Visit replay.io ↗Alternativestop 1% of September 2021

In plain words

Replay is a web development debugger that allows developers to record and replay browser sessions to investigate bugs. Users can step backward and forward through code execution, inspect variables at any point in time, and collaborate with teammates by sharing recordings. It's designed for developers who want a more efficient way to understand what went wrong in their applications without repeatedly reproducing issues.

written from the facts on this page · September 2026

From the sources

Replay pentests your web app on every QA pass now: injection flaws, broken access control, IDOR, the stuff AI-generated code tends to miss. Findings come back as full bug reports, evidence and suggested fix included. Schedule it daily or weekly and skip the "remember to test" step. You wake up to a queue of bugs already triaged. Same projects also test against dev, staging, prod, and localhost, so you're not maintaining separate QA setups per environment.

Security Scan runs a full pentesting pass against your web app — injection flaws, broken access control, IDOR, and cross-tenant data exposure. The vulnerabilities AI coding agents introduce at scale, found automatically.

Does a similar job

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  • Replay2021 · replay.io · ▲279

    Your time travel debugger

  • Replay QAJul 2026 · qa.replay.io · ▲438

    Replay QA tells you what is broken before your users do

  • Time travel debugging AI for more reliable vibe coding2025 · nut.new · ▲129

    Hi HN, I'm the CEO at https://replay.io. We've been building a time travel debugger for web apps for several years now (previous HN post: https://news.ycombinator.com/item?id=28539247) and are combining our tech with AI to automate the debugging process. AIs are really good at writing code but really bad at debugging -- it's amazing to use Claude to prompt an app into existence, and pretty frustrating when that app doesn't work right and Claude is all thumbs fixing the problem. The basic reason for this is a lack of context. People can use devtools to understand…

  • Session Replays by Requestly2023 · requestly.com · ▲518

    Debug web apps faster with record & replay

  • Session Replay by Zarget2017 · ▲338

    See how visitors view and use your site.

  • Progress AI ObservabilityAug 2026 · telerik.com · ▲168

    Hi HN! We’re the team behind Fiddler, and we recently built an Agent Cache feature. It works by capturing an LLM request/response pair and, once caching is enabled, serving subsequent matching calls locally so duplicate requests never hit the provider. It’s meant to reduce three pains that show up together in agent development: token cost, feedback-loop latency, and output non-determinism. We’d love to hear your thoughts.

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Source: Show HN post ↗

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