Read a Mattermost Bulk Export

What this tool does

Paste the import.jsonl file from a Mattermost bulk export and get a readable transcript you can review, archive, search or hand to a migration/audit workflow. The conversion is deterministic and local: the JSON Lines file is parsed in your browser, display names are resolved from the export's user records, and channel posts, direct messages, replies, reactions and attachments are rendered without uploading the archive anywhere.

Mattermost's bulk export is built for imports, not humans. Each line is a separate object tagged with a type such as version, team, channel, user, post, direct_channel or direct_post. This tool indexes the metadata first, then renders the message records with UTC timestamps and friendly labels.

Worked example

Input — a small Mattermost JSONL export:

{"type":"version","version":1}
{"type":"channel","channel":{"team":"core","name":"town-square","display_name":"Town Square","type":"O"}}
{"type":"user","user":{"username":"alice","first_name":"Alice","last_name":"Anderson"}}
{"type":"user","user":{"username":"bob","nickname":"Bobby"}}
{"type":"post","post":{"team":"core","channel":"town-square","user":"alice","message":"Standup in five","create_at":1705311000000,"reactions":[{"user":"bob","emoji_name":"thumbsup"}],"replies":[{"user":"bob","message":"On my way","create_at":1705311120000}]}}

Output — summary plus transcript:

Bulk export format version: 1
Channels in export: 1
Users in export: 2
Messages after filters: 2

--- #town-square (Town Square) ---

[2024-01-15 09:30:00 UTC] Alice Anderson: Standup in five [reactions: :thumbsup:]
    ↳ [2024-01-15 09:32:00 UTC] Bobby: On my way

Options

Limits & edge cases

• Input shape: paste the text contents of import.jsonl, not the .zip/.tar archive. Extract the archive first and open the JSONL file as text.
• Timestamps are UTC. Mattermost stores create_at as Unix milliseconds; this tool renders UTC dates and times so filtering is reproducible.
• Unknown records are ignored. Newer Mattermost export line types do not break the transcript. Malformed JSON, missing type fields and reversed date bounds produce explicit errors.
• Attachments are referenced, not downloaded. The transcript includes [attachment: path] placeholders from the export metadata. It does not unpack or fetch files.
• No deleted/edited-message recovery. The export only contains what Mattermost wrote into the bulk export. This tool does not query a server or reconstruct history outside that file.
• Large exports can be heavy in the browser. Use filters and the max-message cap to preview, then remove the cap for the final transcript.

FAQ