Unlogged – open-source record and replay for Java
Hello HN! Parth, and Shardul here. We have been building unlogged.io for the last 21 months. We started as a time travel debugger and pivoted to record and replay with assertions, mocking, and code coverage. You can save the replays in the form of a JSON and commit them to your git. Both Parth and I come from an e-commerce/payments background where production bugs meant heavy financial losses. Big billion days/Black Friday sales meant months of code freezes with low productivity. Before committing the code, we wanted to replay production traffic and know the breaking changes right…
Unlogged – open-source record and replay for Java launched on October 30, 2023 with 90 votes, #897 of 4,393 launches that month and more than 90% of that year's launches.
In plain words
Unlogged is an open-source record and replay tool for Java that captures code execution and allows developers to replay production traffic with assertions, mocking, and code coverage analysis. It works through an SDK that adds compile-time probes to log execution details, with replays saved as JSON files that can be committed to Git. Designed for teams building e-commerce and payment systems where production bugs carry significant financial risk, it helps identify breaking changes before deployment.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
Hello HN! Parth, and Shardul here. We have been building unlogged.io for the last 21 months. We started as a time travel debugger and pivoted to record and replay with assertions, mocking, and code coverage. You can save the replays in the form of a JSON and commit them to your git. Both Parth and I come from an…
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