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Image Compressor & Converter

Choose a use case and compare PNG, JPEG, and WebP formats, quality, and resolution to balance file size and visual quality.

View on GitHub

Local processing

About your filesFiles and content selected in this tool are processed in your browser and are not uploaded to a Browser Kitty backend.

Operation demo See the basic workflow in a short video.

About this tool

Image Compressor & Converter is an image-optimization workbench for PNG, JPEG, and WebP rather than a simple format converter. Choose a use case, then compare format, quality, and resolution candidates. Smart Optimize evaluates multiple local candidates and selects a smaller result that meets a lightweight visual-quality threshold.

For strict upload limits, target-size mode can reduce resolution when quality changes alone are not enough. Before / After and amplified-difference views help review the result, while Base64, HTML, CSS, Markdown, picture-element output, and web-asset ZIPs are available from the same workflow.

Good for

Make website or README images smaller while visually reviewing the result
Meet limits such as 500 KB by adjusting both quality and resolution when needed
Optimize multiple images and export WebP, picture-element markup, or other web-ready assets

What it can do

Key capabilities available in this tool.

Use-case presets and Smart Optimize
Target-size search across quality and resolution
Before / After and amplified difference
Base64, picture, and web-asset ZIP output

How to use

Add PNG, JPEG, or WebP images. On desktop, Ctrl+V can add copied images or screenshots.
Choose a use-case preset such as website, photo, screenshot, or file-size limit.
Run Smart Optimize, or manually set target size, output format, resize dimensions, and quality when needed.
Review Before / After, amplified difference, original/output sizes, and reduction rate.
Export an individual image, a multi-image ZIP, or Base64, HTML, CSS, Markdown, picture markup, or a web-asset ZIP.

Supported

Input/output: PNG, JPEG, and WebP. Desktop supports Ctrl+V paste, and file selection supports multiple images.
Optimization: use-case presets, Smart Optimize, plus detailed format, quality, and resize controls.
Target size: JPEG/WebP can vary quality and resolution; PNG can reduce resolution to search below the requested KB limit.
Export: individual images, ZIP with folder structure, Base64, HTML, CSS, Markdown, picture markup, and web-asset ZIP.

Limitations and notes

PNG output is lossless. In target-size mode, PNG reduces resolution rather than quality to reach a smaller size.
The Smart Optimize visual score is a lightweight heuristic for candidate selection, not a professional image-quality metric.
Canvas re-encoding removes metadata such as EXIF, and animated-image animation is not preserved.
Browser encoders differ, and very large images or large batches can consume significant device memory.

Frequently asked questions

Are images uploaded to a server?

No. Loading, Smart Optimize, comparison, and export run in the browser; selected images are not sent to Browser Kitty.

What does Smart Optimize choose automatically?

It compares JPEG, WebP, PNG, and multiple quality candidates locally, then picks a smaller result among candidates meeting a lightweight visual-quality threshold. You can still lock format or quality in advanced settings.

Can it target a specific file size?

Target-size mode accepts a KB limit. JPEG/WebP can lower quality and then resolution; PNG uses resolution reduction because it is lossless. A particular image may still make an exact limit impossible to guarantee.

What happens if the converted image is larger?

By default, the original is kept when the converted result would be larger. You can disable that behavior when changing format is more important than size reduction.

Offline version and source code

The root-level image-compressor-converter.html on GitHub is a self-contained single HTML file that can be saved and opened locally for offline image compression and conversion.

View source on GitHub