Preview

The preview panel renders the focused object in the active pane. brows3r chooses a renderer based on MIME type first, then falls back to file extension — this matters because S3 frequently stores objects with Content-Type: application/octet-stream (the default when aws s3 cp runs without --content-type).

Routing

Renderer	MIME / extension
Image	image/*, .png .jpg .jpeg .gif .webp .svg .bmp .ico .tif .avif .heic
Video	video/*, .mp4 .m4v .mov .webm .mkv .avi .ogv .3gp .mpg .wmv .flv
Audio	audio/*, .mp3 .wav .ogg .flac .aac .m4a .opus .wma .aiff
PDF	application/pdf, .pdf
HTML	text/html, .html .htm .xhtml — sandboxed iframe + "View source" toggle
Markdown	text/markdown, .md — GFM + syntax highlight
Archive	application/zip, .zip .tar .gz .tgz .tar.gz — entry listing, no in-app extract
Table	.csv .ndjson .jsonl .parquet or top-level JSON arrays
Text / code	text/* + extension-mapped languages — Shiki syntax highlight
Hex	.bin .exe .dll .so .dylib .wasm .obj .o .a .lib (known binaries)

Anything that isn't matched to a specific renderer falls through to Text as a best-effort: the backend UTF-8 decodes the bytes, replacing invalid sequences with U+FFFD. If the result looks like noise, switch to Hex from the preview toolbar.

Size limit

Previews are capped at 50 MB (configurable in Settings → Preview). Larger objects show a "Preview anyway" button — clicking it bypasses the cap for that file. This is on top of the 1 MB text-fetch cap built into object_get_text (the backend Range-reads the first MB and replaces invalid bytes — a "Truncated" banner appears in the preview).

Text & editor options

The Shiki-rendered text view and the Monaco editor share a settings popover (gear icon in the toolbar). Preferences persist in useUiStore.textPreviewPrefs:

• Theme: auto (follows the global UI theme) / light / dark
• Word wrap: on / off (affects both Shiki and Monaco)
• Font size: 9–28 px stepper
• Line numbers: editor-only (toggle visible in the popover)

The "Edit in Monaco" button on a text preview switches to the editor with the same theme/wrap/font preferences. Save (Cmd+S) goes through object_put_text with an If-Match ETag precondition — on conflict you get an inline "Refresh / Save anyway" banner.

Media (image / video / audio / PDF)

Media bytes never cross the IPC boundary. The flow is:

1. Component calls mediaRegister(profileId, bucket, key) over IPC.
2. Rust mints a single-use session token + returns a loopback URL (http://127.0.0.1:<port>/m/<token>).
3. The HTML element (<img>, <video>, <audio>, <iframe> for PDF.js via react-pdf) loads bytes from the loopback server.
4. The Rust server validates the token, streams from S3 with a Range request, and forwards bytes to the WebView.

The loopback server emits Access-Control-Allow-Origin: * so that fetch()-based renderers (pdf.js) can read responses cross-origin from the WebView. Tokens are unguessable and revoked on component unmount; see Concepts → Media server for the threat model.

"Fetched X ago"

The status bar shows when the object's HEAD was last fetched. Useful for spotting stale previews after a concurrent upload — the bar re-renders every 15 seconds, and the tooltip carries the absolute timestamp.