Filestay
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Image converter

Move between JPG, PNG, WebP, AVIF and HEIC without sending anything to a server. Pick an output format and go.

  • 0 uploads
  • No limits
  • No signup
  • Works offline

The five formats, briefly

JPEG (1992) is the universal one. Every device, browser, printer, form and photo kiosk on earth reads it. It is lossy, has no transparency, and is nobody’s idea of efficient — but it always works, which is worth a great deal.

PNG (1996) is lossless with full alpha transparency. Perfect for screenshots, logos, diagrams and anything with sharp edges or flat colour. Terrible for photographs, where it produces files several times larger than a JPEG that looks the same.

WebP (2010) is Google’s replacement for both. It does lossy and lossless, with transparency, and sits roughly 25–35% below JPEG at matching visual quality. Support is now universal in browsers, though some desktop applications and older phones still stumble on it.

AVIF (2019) is the current efficiency champion, based on the AV1 video codec. Roughly half the size of JPEG at similar quality, with transparency and HDR. The trade-off is encoding time and patchier support outside browsers.

HEIC (2015) is Apple’s default camera format, built on HEVC. Excellent compression, poor compatibility outside the Apple ecosystem, which is why HEIC to JPG is the single most-requested conversion there is.

A practical decision table

You are doing this Convert to
Uploading to a government or university form JPG
Sending a photo to someone on Windows JPG
Putting images on your own website WebP, with a JPG fallback
Sharing a screenshot with text in it PNG
Making a logo or icon with transparency PNG or WebP
Squeezing the last bytes out of a hero image AVIF
Archiving originals keep the original; convert copies

What runs under the hood

Decoding uses your browser’s own image pipeline where it can, and WebAssembly builds of libheif and libavif where it cannot. Encoding uses MozJPEG, libwebp, libavif and OxiPNG — the same set that powers Squoosh — all compiled to WebAssembly and executed in a Web Worker so the page stays responsive while a large batch runs.

Every one of those modules is fetched once, cached by the service worker, and then works offline forever. Your images are only ever read from your own disk and written back to it.

Format pairs with their own pages

Each of these opens the converter preconfigured, and explains the specific trade-off involved:

PNG to JPG · JPG to PNG · WebP to PNG · PNG to WebP · WebP to JPG · JPG to WebP · AVIF to JPG · AVIF to PNG · JPG to AVIF · HEIC to JPG · HEIC to PNG · HEIC to WebP

How it works

  1. 01Add your imagesDrop, click, paste or drop a folder. Mixed input formats in one batch are fine.
  2. 02Choose the output formatJPG for compatibility, PNG for transparency, WebP for the best size-to-quality ratio, AVIF for the smallest files.
  3. 03Set qualityLossy formats get a quality slider. PNG gets an optional lossless OxiPNG pass instead.
  4. 04DownloadSave individually or take the whole batch as a zip built on your device.

Questions people actually ask

Which format should I actually use?
JPG when something else has to open it — forms, email, printing, anything old. PNG when you need transparency or pixel-exact screenshots. WebP for your own website, where it is typically 25–35% smaller than JPEG at matching quality. AVIF when size matters more than universal support.
What happens to transparency when I convert PNG to JPG?
JPEG has no alpha channel, so transparent areas have to become a colour. The converter flattens them onto white by default, and lets you pick a different colour. If keeping transparency matters, convert to WebP or AVIF instead — both support it.
Why is AVIF so slow to encode?
AVIF is a still frame of an AV1 video, and AV1 encoding is genuinely expensive — it searches a much larger space of prediction modes than JPEG does. A 4K image can take ten seconds or more. The payoff is files roughly half the size of an equivalent JPEG.
Can I convert HEIC here?
As an input, yes — HEIC and HEIF files are decoded with libheif and can go out as JPG, PNG, WebP or AVIF. We do not write HEIC, because almost nobody needs to create one and the encoder carries patent complications.
Does converting lose quality?
Converting between two lossy formats (JPG → WebP, HEIC → JPG) re-encodes and loses a little. Converting a lossy source to PNG is lossless from that point on but cannot recover what the original encode already discarded. Converting PNG → PNG is exactly lossless.
Is there a limit?
No. Nothing is uploaded, so there is no bandwidth to pay for and nothing to meter. Batch size is bounded by your device’s memory, not by us.

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