UtilityKit

500+ fast, free tools. Most run in your browser only; Image & PDF tools upload files to the backend when you run them.

Bulk Image Convert

Convert many images between JPG, PNG, and WebP and download as a ZIP

About Bulk Image Convert

Sometimes resizing is overkill — you already have the right dimensions, you just need a different format. This tool converts a folder of mixed images into one uniform format (JPG, PNG, or WebP), packs the results into a single ZIP, and lets you download it without uploading a single byte. Sources can mix formats freely; targets are uniform. A quality slider applies to lossy formats, and a JPG fill color handles transparent inputs gracefully so you never get unexpected black backgrounds. A filename suffix lets you sort the output apart from the originals when extracting back into the same folder. The pipeline runs on Canvas re-encoding plus JSZip locally, with no daily limit, no signup, and no watermark. Useful for moving sites to WebP, flattening transparent PNGs to JPG for email, or collecting a Slack drop of mixed phone screenshots into one archive.

Why use Bulk Image Convert

One Output Format from Mixed Sources

Drop in 30 PNGs, 20 JPGs, and 10 WebPs and get back 60 uniform files. The pipeline normalises any common image input into the format you choose, with no manual sorting.

JPG Fill Color Avoids Black Corners

Converting a transparent PNG to JPG without a fill color produces black corners where the alpha used to be. The dedicated fill picker lets you choose white, brand color, or anything else — avoiding the most common gotcha.

Browser-Only — No Upload, No Quota

Everything runs locally via Canvas and JSZip. Files never leave the page, no account needed, no daily limit, no watermark.

Quality Slider for Lossy Formats

1–100 control over JPG and WebP encoding. PNG is lossless and ignores the slider. Default 85 is the conservative web sweet spot.

Filename Suffix for Output Organization

Add "-web" or "-converted" to keep the new files visually separate from the originals when both extract into the same folder.

Streaming Pipeline — Low Memory Peak

Each image is decoded, re-encoded, and written into the ZIP one at a time. Memory stays flat even for hundreds of images.

How to use Bulk Image Convert

Pick multiple images at once — formats can mix freely (JPG, PNG, WebP all together).
Select the target format you want every output to use.
If the target is JPG, choose a fill color for any transparent areas.
Set the quality slider for lossy formats; PNG ignores it.
Add an optional filename suffix (e.g. "-web") so the new files sort apart from the originals.
Click Convert — the progress bar updates as each file is encoded; the ZIP downloads when complete.

When to use Bulk Image Convert

When moving a website's existing JPG and PNG asset library to WebP for Core Web Vitals improvements.
When flattening transparent PNG logos to JPG with a brand-color background for email signatures or document headers.
When a stakeholder asks for a folder of "all the images as JPGs" but the source is a mix of formats.
When archiving a Slack drop or phone export with mixed PNG/JPG/WebP files into a single uniform ZIP.
When prepping a portfolio for a job application that requires a specific format only.
When converting screenshots from PNG (default on macOS) to lossless WebP to save space without quality loss.

Examples

Site migration to WebP

Input: 150 mixed JPG and PNG assets, 380 MB total

Output: All converted to WebP quality 85 with -web suffix, packed in 110 MB ZIP

Transparent logos to JPG

Input: 12 PNG logos with transparency

Output: Converted to JPG quality 92 with #ffffff fill color — clean white-background outputs in a 4 MB ZIP

Slack drop normalization

Input: 30 mixed phone screenshots (PNG, JPG, HEIC)

Output: All converted to PNG (lossless) with no quality loss, packed in 64 MB ZIP

Tips

WebP at quality 85 is the most reliable web default — supported in all modern browsers since 2020.
When converting transparent PNGs to JPG, set the fill color to match the destination page background so the result blends seamlessly.
PNG is lossless — the quality slider has no effect. Choose PNG only when you need transparency or perfect edge fidelity.
Use "-web" as the suffix when prepping for production deployment, and "-archive" when storing long-term backups.
If your sources have wildly different dimensions, pair this with the bulk batch tool to also enforce a max bounding box.

Frequently Asked Questions

Why does my converted JPG look weird around the edges?▾

If the source was a transparent PNG, the alpha channel was filled with the chosen fill color. If you see unexpected colors, change the fill color to match your destination page background.

Can it convert HEIC files?▾

Browser HEIC support is patchy. Safari can decode it; Chrome and Firefox cannot. For reliable HEIC input, run heic-to-jpg first then come back here for further format changes.

Is the quality slider applied to PNG?▾

No. PNG is a lossless format — encoder settings only affect compression speed, not output quality. The slider value is ignored when PNG is the target.

How big a batch can I process?▾

There is no hard limit. The streaming pipeline keeps memory flat. Hundreds of files complete reliably; for very large batches (1000+) split into multiple passes for tab responsiveness.

Does it strip EXIF metadata?▾

Yes. Re-encoding through Canvas removes EXIF, XMP, and IPTC metadata. If you need to keep camera or copyright fields, use a tool that preserves metadata explicitly.

Are originals modified?▾

No — they are read once and never written back. The processed copies are packed into the downloaded ZIP under new filenames.

Is there a watermark on output?▾

No watermark, no logo, no upsell. The output is your images in the new format only.

Are my files uploaded?▾

No. The entire conversion runs locally via Canvas and JSZip. No image bytes leave your browser at any point.

Explore the category

Glossary

Lossy compression: An encoding scheme (JPG, WebP, AVIF) that discards information to reduce file size. Quality is configurable via a slider, with 80–85 being the typical web sweet spot.
Lossless compression: An encoding scheme (PNG) that reduces file size without discarding any pixel data. Decoded pixels are bit-identical to the source. Larger files than lossy at equivalent visual quality.
Alpha matting: Compositing a transparent PNG onto a solid background color so it can be saved as JPG, which has no alpha channel. The fill color picker controls what shows through previously transparent pixels.
WebP: An image format developed by Google offering 25–35% smaller files than JPG at equivalent visual quality. Universal browser support since 2020.
PNG-24: A 24-bit-per-pixel PNG with optional 8-bit alpha channel. Lossless and supports transparency. Larger than JPG for photos but ideal for screenshots and graphics.
Re-encoding: Decoding an image to raw pixels and re-encoding into a target format. Re-encoding always strips metadata (EXIF, ICC) and produces a new file.