LAPLACE Chat

Overview

LAPLACE Chat Archive (.lca for short) is a compressed event archive format used for:

• Cross-device migration: sync your full event history between your main machine and your backup machine
• Long-term backup: avoid losing important events when the browser clears IndexedDB
• Offline analysis: import archives into data analysis tools for further processing

New Archive Format

Since May 14, 2026, .lca archives use standard gzip compression, and are already prepared for the future zstd format

Compared with the old proprietary compression format (introduced in #64), the new format offers:

• Faster export / import: uses native browser APIs
• Higher compression ratio: standard gzip typically uses over 30% less space than the old format

Archive Converter

Go to /lca-convert to use the archive converter:

• Drop a .lca onto the page and its format is detected automatically
• The tool decompresses and recompresses locally in the browser, and uploads nothing
• Download the new-format archive once the conversion finishes and use it to replace the original file

Exporting an Archive

• Open the settings panel in the dashboard sidebar
• Scroll to the Database Management and Import & Export sections
• Pick the LAPLACE Chat Archive (.lca) format under Export Events…
• Click export to download a <roomId>_<uname>_<exportDate>.lca file

Other Export Formats

Besides .lca, the dashboard supports the following export formats:

Importing an Archive

• Open the settings panel in the dashboard sidebar
• Scroll to the Import Events… section
• Drop the .lca file onto the upload area, or click to pick a file
• The dashboard detects the archive format and decompresses it automatically

Browser Compatibility

• Exporting a .lca archive relies on the browser's native CompressionStream('gzip') API
• That API has been available in every major browser since May 2023 (Chrome 80+, Firefox 113+, Safari 16.4+)
• If your browser is too old to export .lca, upgrade to the latest version

Data Storage

• Every event is stored in the browser's IndexedDB (the eventItems table)
• Clearing browser data also clears every local event, so export a .lca backup regularly
• IndexedDB is not shared between browsers (Chrome / Firefox / Safari / Edge)

Related Features

• User Notes: notes are separate from the event archive and must be imported and exported separately (.lcun format)
• User History: local event data backed by IndexedDB