Batch Image Format Converter

Convert multiple images between PNG, JPG, WebP, and AVIF in one batch with ZIP output.

Tested tool guide Tested browser tools Checked August 15, 2026

What Batch Image Format Converter does, with a checked example

This tool takes a batch of images you drop in - any mix of PNG, JPG, WebP, or AVIF source files - and re-encodes each one into whichever target format and quality you choose, then bundles all the results into a single ZIP you download in one go. Conversion happens by drawing each image onto a canvas and exporting it in the new format, so files never leave your browser. The most common surprise: AVIF encoding isn't supported in every browser, and converting a PNG or WebP with transparency to JPG silently fills the transparent areas solid, since JPG has no alpha channel.

Worked example

A concrete input and expected output from the current implementation.

Input

3 files dropped in: photo1.png, photo2.png, icon.png (icon.png has a transparent background) - target format WebP, quality 80

Expected output

download.zip containing photo1.webp, photo2.webp, icon.webp, each re-encoded at quality 80. icon.webp keeps its transparent background.

Base filenames are preserved, only the extension changes to .webp - but the pixel data itself is not untouched, since quality 80 is a lossy WebP setting and canvas re-encoding also drops metadata such as EXIF tags and embedded color profiles. WebP supports an alpha channel like PNG, so icon.png's transparency carries over intact, which would not happen if the target were JPG.

How the result is produced

Decode-then-re-encode per image

Each source file is loaded into the browser and drawn onto an off-screen canvas, then exported through the canvas's blob-encoding step with the target format and quality you set. This is why the tool can convert between any of PNG, JPG, WebP, and AVIF in either direction - it isn't rewriting file headers, it's fully decoding pixels and re-encoding them.

Batch queue with single ZIP output

Instead of triggering a separate download per file, the tool processes the whole batch and packages every converted output into one ZIP archive, offered as a single download. Original filenames are kept with the new extension swapped in, so you can match outputs back to inputs after unzipping.

Good uses

Converting a folder of PNG screenshots to WebP to cut file size before adding them to a website
Converting a batch of JPG photos to AVIF for smaller long-term storage
Normalizing a mixed folder of PNG, JPG, and WebP images into one consistent format before uploading elsewhere

Limits and checks

AVIF encoding support varies by browser - decoding AVIF is common, but not every browser can encode it, so an AVIF target may fail or silently fall back depending on what you're running
Converting a lossy source (JPG) into another lossy format (JPG or AVIF again) does not undo the quality already lost in the original - it adds a further round of compression on top
Transparency is lost on any conversion to JPG, since JPG has no alpha channel; transparent pixels typically become solid white or black rather than staying see-through

Common questions

Will converting PNG to JPG always make the file smaller?

Usually for photos, but not guaranteed. Screenshots, graphics, or images with large flat-color areas or transparency can end up looking worse or not much smaller in JPG. WebP or AVIF at the same visual quality will usually beat both PNG and JPG on file size.

How many images can I convert in one batch?

There's no hard-coded limit, but everything runs in your browser tab's memory, so very large batches or very large source images can slow the tab down or cause it to run out of memory. Dozens of typical web-sized images at a time is a safe range; thousands is not.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.