How conversion works
Convert mode is a registry of pairs, not a magic “any file → any file” box. Each converter registers the exact from→to keys it implements. If a pair is not in the registry, Shrynk will refuse it instead of guessing.
That registry is the ConvertET engine now shipped inside Shrynk: data, image, document, audio, video, and ebook modules share one UI — format cards, file list, options panel, task manager, history.
The job loop
- Select a pair (grid, category filter, or search).
- Add files that match the source side. Wrong extensions are rejected at validate time.
- Set options. The panel is generated from that pair’s schema — you never see SVG background color on an MP3→WAV job.
- Start. The task manager runs files with a concurrency cap you can change in settings.
- Open the output folder from the result or from History.
What each category actually changes
| Category | Engine | Typical options |
|---|---|---|
| Data | Pure Go | CSV delimiter; TXT source/target encoding (UTF-8, GBK, GB2312) |
| Image | Pure Go | JPEG quality; width/height; keep aspect; SVG background; ICO sizes |
| Document | Pure Go | Markdown → HTML can embed default CSS; Markdown → DOCX keeps headings, lists, code blocks |
| Audio | Bundled FFmpeg | Bitrate on lossy outputs; sample rate |
| Video | Bundled FFmpeg | Quality preset; resolution; GIF fps/width; extract-audio bitrate |
| Ebook | Calibre ebook-convert | Embed fonts; pair must be one of the registered ebook routes |
Remux vs re-encode
Changing a container (MOV → MP4) without re-encoding barely changes size. Shrynk video convert re-encodes so the output is a normal, playable file with the quality/resolution you picked. If you only wanted a smaller file and the container is already MP4, use Compress instead of Convert.
Hard limits that are not bugs
- No PDF → Word. PDF is an output of some ebook routes, not an Office importer.
- Markdown is one-way into HTML and DOCX. There is no DOCX → Markdown converter in this build.
- Conversion file size is capped per file (500MB in the current build) so a runaway encode cannot fill the disk unnoticed. Compress Pro is the path for multi‑GB camera files.
- Free vs batch is a license rule, documented on Free vs Pro.
Browser preview (not the registry)
The homepage box converts a short allowlist of stills in the tab: WEBP→JPG/PNG, PNG↔JPG, PNG/JPG→WEBP, GIF→PNG (first frame), SVG→PNG. One file, about 25MB, no upload. It is not the 200+ pair registry. Audio, video convert, extract, ICO, ebooks, Markdown, and data stay in the Windows app.
WEBP encode differs. The browser writes a real WebP (RIFF/WEBP via canvas.toBlob). This Windows build still writes PNG bytes under a .webp name. Decode WEBP is real on both. See PNG to WEBP.
The full pair list lives on Supported formats. For folder-scale runs, see Batch jobs.