OmniFile: batch conversion that reads the bytes, not the name

What it is, and who it is for

OmniFile is a batch converter that runs in the browser tab. Drop files, a folder or a ZIP, or paste a direct link; it reads what each file really is from its bytes, then converts images and text through the browser’s Canvas and audio and video through FFmpeg compiled to WebAssembly. Nothing is uploaded.

It is for anyone converting a batch of photos, clips or data files who would rather not send them to an online service.

How it works

The code’s first lines set the rule: no file you pick is ever sent anywhere, and there is no endpoint on the property to send one to (app.js lines 1–10). A sniffer names each file from its first bytes — about 45 identities, HEIC variants told apart by their ftyp brand — and says so when a name lies (lines 186–349). Readers parse headers for measured facts, among them EXIF orientation and whether a photo carries GPS tags; the GPS values themselves are never read or printed, and the page warns that a Canvas re-encode destroys them (lines 509–517).

The most unusual step comes before any conversion is offered: OmniFile tests the browser in front of it. It encodes a one-pixel canvas as PNG, JPEG, WebP and AVIF and sniffs what actually came out; it decodes tiny PNG, WebP, AVIF, HEIC and TIFF samples with both of the browser’s decoders, because they have been known to disagree; and it finds the largest canvas edge that really paints (lines 940–1035). FFmpeg — @ffmpeg/ffmpeg 0.12.10 with core 0.12.6 — comes from unpkg.com only when you ask for it, its addresses named on the page first.

• What it reads
• No data sources: files are read from your own disk
• unpkg.com: the FFmpeg class, worker and WebAssembly core, fetched on demand — code coming in, never files going out
• Bundled: jszip.min.js
• A direct link you paste, fetched by the tab from the host that serves it

What we measured, and when

At 20:17:30 UTC the page came back from the local copy at 85,877 bytes, its script at 275,289 bytes and JSZip at 97,630 bytes. We then fetched the FFmpeg core the page asks for from unpkg: 32,129,114 bytes in 0.40 seconds on our connection, which matches the code’s own warning that “a 32 MB fetch should never be a surprise”.

The first screen (captured 20:15:04 UTC) describes the same engine as “about ten megabytes of compiled FFmpeg” — callout 4. We measured the uncompressed core, not what crosses a compressed connection, so we cannot say which figure a visitor will see on the wire; we can say the page and its code give two different sizes. We did not run a conversion, which needs a real browser.

390 × 84420:15:09Z

12

Beside CloudConvert and Squoosh

Each comparator was checked on the date shown. We say what each does better before we say where OmniFile goes further.

Where it falls short

• Documents are named but not converted: PDF, Office, OpenDocument, EPUB, RAR, 7-Zip, gzip, fonts and Photoshop files are ones the desk “can name but not convert”. CloudConvert handles 212 formats.
• Audio and video need a 32 MB WebAssembly download from a third-party CDN on first use; if unpkg.com is unreachable, so is every audio or video conversion.
• Heavy video work runs on your machine inside a tab, so speed and size limits depend on your device.
• What it can read depends on your browser: HEIC, AVIF and TIFF decoding is tested per browser and may be missing.

The verdict