Bring your data.
Order-book replay in your browser: import a session you downloaded from Tardis.dev and step through it event by event. The file never leaves your machine.
The public demo runs in the browser: no account, no install. The app is invite-only. What is order-book replay?
- Live demo
- Free to try
- No account
- Opens in the browser
- No install
- Nothing to download
- Your own data
- Tardis.dev files
Replay is a debugging and inspection tool, not a backtesting or execution platform.
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Review an execution
You can't review a fill you can't see again.
By the time you go looking, the book that produced your fill is gone. Replay reconstructs it. Move the cursor to the moment of the fill and read the ladder as it stood, then step backward through the updates that got it there.
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Precision
Prices survive the round trip.
Parse an exchange export into floating point and the values quietly stop matching the venue. Replay stores prices and sizes as exact decimals, and computes spread and midpoint with exact decimal arithmetic. Some display figures, such as book imbalance and the depth chart, use ordinary numbers.
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Reproducibility
Same session, same cursor, same state. Every run.
Deterministic replay is what lets you check a result instead of guessing at it. Put the cursor on a timestamp and the reconstructed state is identical every time you return to it, on every machine that loads the same session. That is the property you need before a replay result means anything.
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Depth
Read the full ladder, not the last price.
Playback that shows you a single price tells you what happened and not why. Replay renders the full bid and ask ladder with the spread, so you can watch depth thin out ahead of the move instead of inferring it afterward.
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Evidence
A session is a file, not a screenshot.
Every session travels as one self-contained artifact: metadata, state, time range, source provenance, and the bookmarks that flag what mattered. It is versioned, so the session you reopen next quarter is the one you reviewed today. Sessions can be exported.
Follow the state, not just the latest update.
Replay the session in order, then inspect the exact state at the moment that matters.
- 01
Load a session
Start with the built-in deterministic demo data or load a recorded session.
- 02
Move through time
Move backward or forward to any retained timestamp, event by event.
- 03
Inspect the state
Inspect the exact order-book or candle state at any event. Export the session with its source provenance.
Under the hood Verified technical details
Exact decimals for spread and midpoint Prices and sizes are stored as strings. Spread and midpoint use fixed-point decimal arithmetic; imbalance and depth-chart figures use ordinary numbers.
L1 / L2, top or full depth Inspect the top of book or the full retained ladder, with the spread.
OpenCandle schema-aware replay The engine reads OpenCandle V1 — tuple feeds and JSON records.
Step and seek, both directions Step event by event, backward or forward, or jump to any retained timestamp.
Continuous playback Play a session at a chosen speed. The fastest speed offered is measured on your device.
Bring your own recorded session Import Tardis.dev order-book CSVs or OpenCandle V1 files. They stay in your browser.
Provenance travels with the session Provider, channel, symbol, and capture time are carried on export.
Deterministic reconstruction Same session, same cursor, same state — replayed from the nearest snapshot through diffs.
Live connection The demo does not connect to a live feed today.
Built by someone who worked on replay before.
Matchstick Replay is a tool I wanted for years. I was a product manager at a futures trading platform, where I worked on its market replay and tick replay. It started with customer discovery, interviews, bug reports and QA on the older replay, to understand what was broken and what traders needed.
More about the founder- Product manager
- Futures trading platform
- Replay
- Worked on market replay and tick replay
Invite-only preview
The professional app now runs beside the demo.
The professional app is in invite-only preview at app.matchstick.trading. It does one job: open a session from your own machine, check it, move through it by event or by timestamp, see the reconstructed book and where the data came from — then close the browser and reopen the same session without ever uploading it.
That is the whole scope for now. Access is by invitation: ask for an account at app.matchstick.trading and a person will reply. No plans or payments yet. To hear when it grows, use the list below.
Join the notification listHear about it when there's something new to replay.
One confirmation now, then one email when Replay ships something worth your time. Not a newsletter. Unsubscribe whenever.
What would you replay?
One specific answer beats a dashboard of vanity metrics. Tell me the session you need to replay. Contact details are optional.