📂 Open files easily — click the Open file button (native OS file picker), drag & drop files anywhere on the page, or pass files/directories to the CLI. Files opened in the browser are parsed locally — nothing is uploaded
📄 Raw view — toggle the Raw button (or press v) to see each line exactly as it is on disk, with search highlighting intact
🔃 Sorting — click any column header (time, level, message, dynamic columns) to sort ascending → descending → off
⏱️ Last N filter — one-click menus for "last 1/5/15/30/60 minutes" or "last 50/100/500/1000 lines"
⬇️ Follow mode — auto-scrolls to the newest lines while live tailing (button, f key, or -F CLI flag); scrolling up pauses it automatically
🕘 Recent files — sidebar remembers the last 10 opened files; in Chromium they reopen with one click (via the File System Access API), elsewhere server/CLI files reopen by path and browser files are dimmed when unavailable
🚫 Drop dedup — dropping the same file twice never duplicates it
⚡ Streaming parse — handles huge files, everything stays in your browser
🔍 Search — substring or regex (.* toggle), with match highlighting
🎛️ Auto-detected columns — timestamps, levels, messages and any recurring fields become columns automatically
🏷️ Facets — one-click filters for low-cardinality fields (direction, kind, method, status…)
📊 Time histogram — stacked by log level, drag to zoom into a time range
🐛 Row inspector — collapsible JSON tree, raw view, copy JSON / raw
🔴 Live tail — follows your file like tail -f while your app writes to it (SSE, auto-reconnect, truncate-safe)
🎨 Dark / light theme, keyboard-driven (/ search, j/k navigate, Enter inspect, Esc close)
🚀 Works with any JSONL — auto-detects timestamp/ts/time, level/severity, message/msg/event, and more

Install

npm install -g jsonlviz

or run it ad-hoc:

npx jsonlviz <path>

Usage

jsonlviz                                # open viewer in drag & drop mode
jsonlviz app.log.jsonl                  # open one file (live tail on)
jsonlviz ~/logs                       # register every *.jsonl under a directory
jsonlviz --port 9000 a.jsonl b.jsonl    # multiple files, custom port
jsonlviz --no-open                      # don't launch a browser
jsonlviz -F ~/logs/app.log.jsonl        # start with Follow (auto-scroll) enabled
jsonlviz --no-watch                     # disable live tail

Flags:

flag	description
`-p, --port <n>`	port (default 7777; auto-increments if busy)
`--host <h>`	bind host (default 127.0.0.1)
`--no-open`	don't auto-open the browser
`-F, --follow`	start with Follow (auto-scroll to newest lines) enabled
`--no-watch`	disable live file tailing
`-v, --version` / `-h, --help`	the usual

Security: the server only serves the files you explicitly registered on the command line — no arbitrary filesystem access, and it binds to localhost by default.

Keyboard shortcuts

key	action
`/`	focus search
`j` / `k` or `↓` / `↑`	move selection
`Enter`	inspect selected row
`Esc`	close drawer / clear search
`g` / `G`	jump to top / bottom
`v`	toggle raw line view
`f`	toggle follow (auto-scroll)
click column header	sort asc → desc → off
drag on histogram	zoom into time range (double-click resets)