Convert Image Format

What each format is for

Every format trades something away. Knowing which trade you want makes the choice quick.

Choosing an output format

For a photograph, JPG is usually the right answer. A phone photo is often 2-5 MB as HEIC or JPG, and re-encoding at a moderate quality setting keeps it visually similar while cutting the size. Text and sharp edges suffer first, so avoid JPG for anything with fine lines.

For a logo, icon or screenshot, use PNG. It keeps hard edges clean and preserves transparency, which JPG cannot store at all. A transparent background turns into a solid colour the moment you save as JPG.

For the web, WebP is the practical default. It supports transparency, handles both photos and graphics reasonably well, and every current major browser reads it. AVIF goes smaller still at the same visual quality, but encoding takes longer and very old software may not open it.

HEIC is what iPhones write by default. It saves space on the phone but many websites, content management systems and desktop programs still reject it. Converting HEIC to JPG is the usual fix when a file will not upload.

Transparency and background colour

Transparency survives only between formats that support it. PNG, WebP and AVIF all carry an alpha channel. JPG does not. If you convert a transparent PNG to JPG, the empty area is filled with a background colour, usually white. Choose that colour deliberately if the image will sit on a dark page, or keep PNG or WebP instead.

Going the other way is safe: a JPG converted to PNG gains no transparency, but it loses nothing either.

Quality settings and file size

Quality only applies to lossy output. JPG, WebP and AVIF all discard some detail to save space, and the amount is controlled by the quality value. Higher values keep more detail and produce larger files. Lower values shrink the file and introduce visible blocking, especially in smooth gradients like skies.

PNG is compressed without that trade-off, so there is no quality slider for it. The file is simply larger.

A sensible workflow: convert first at a moderate quality, look at the preview, and only raise the value if you can see artefacts around edges or in flat areas. Converting repeatedly between lossy formats stacks the loss each time, so keep the original file and convert from it rather than from a previous conversion.

Converting several images

If you have a batch, convert the most demanding image first to find a quality setting you are happy with, then apply the same setting to the rest. Screenshots and graphics usually want PNG or WebP, while camera photos want JPG or AVIF, so split the batch by content type before converting.

Privacy and offline use

The conversion runs in your browser using JavaScript. Your images are never uploaded to a server, nothing is stored, and there is no account to create. Once the page has loaded, it keeps working without a network connection, and the output carries no watermark.

Questions