Question 1

How does the image compressor work?

Accepted Answer

When you upload an image, it is decoded by your browser via FileReader and drawn onto an HTML Canvas. We re-encode the canvas to a Blob via canvas.toBlob(format, quality), which is the native browser-level compression — the same encoder used when saving images out of Photoshop's Save for Web. The compressed Blob is then offered as a download. Everything happens locally; there is no fetch, no XHR, no server processing. You can verify by opening DevTools → Network, uploading an image, and observing that no requests are made.

Question 2

Why does WebP compress better than JPEG?

Accepted Answer

WebP uses a more sophisticated compression algorithm — specifically VP8-based intra-frame coding adapted from video compression — that handles smooth gradients and complex textures more efficiently than JPEG's DCT-based approach. At the same visual quality, WebP files are typically 25-35% smaller than JPEG. WebP also supports alpha transparency, which JPEG does not, so it can replace PNG for graphics with transparency at a fraction of the size. As of 2026, every major browser supports WebP natively, and most CDNs serve WebP variants of JPEG-uploaded assets automatically.

Question 3

Will my image quality suffer at 75%?

Accepted Answer

For photographs at 75% JPEG quality, the visible difference vs the source is typically imperceptible at normal viewing distance — even side-by-side. Artefacts become noticeable at 50% and below, especially in flat-color regions and around sharp edges. For body images on web pages, 75-85% is the standard balance; 92% is appropriate for hero images and content that will be inspected closely. PNG quality slider is not meaningful because PNG is lossless — savings only come from downscaling the dimensions.

Question 4

Can I compress images in bulk?

Accepted Answer

This tool compresses one image at a time to keep the UI simple and the byte comparison precise. For bulk processing of dozens or hundreds of images, dedicated CLI tools like ImageMagick, mozjpeg, or sharp (via Node.js script) are more appropriate. The same Canvas-based pipeline used here can be looped programmatically — see the source code of this tool for the exact algorithm.

Question 5

Why is my compressed file LARGER than the original?

Accepted Answer

A few common causes: (1) the original was already heavily compressed (a 30%-quality JPEG re-encoded at 75% will gain size, not lose it); (2) you converted PNG to JPEG and increased quality above where the PNG was implicitly stored; (3) the source had a very small file size already (under 50 KB) and the format overhead dominates. For pre-compressed images, you cannot reliably reduce size without significant visible quality loss — start with the highest-quality original you have access to.

Question 6

Should I use PNG, JPEG, or WebP?

Accepted Answer

PNG for screenshots, logos, line art, and any image with text or sharp edges — PNG is lossless so text stays crisp. JPEG for photographs and complex imagery with smooth gradients — JPEG's lossy compression is invisible on natural images at 75%+. WebP as a modern replacement for both — it does photographic content better than JPEG and graphics with transparency better than PNG, all in one format. The rule of thumb: ship WebP as primary with JPEG or PNG fallback if you need to support very old browsers (rare in 2026).

Question 7

What about AVIF?

Accepted Answer

AVIF (AV1 Image File Format) is the next-generation image format — typically 30-50% smaller than WebP at the same visual quality, with full alpha and HDR support. Browser decoding is universal in 2026 (Chrome 85+, Firefox 93+, Safari 16+). The catch: canvas.toBlob does not emit AVIF natively in most browsers as of early 2026, so this tool focuses on JPEG/WebP/PNG. For AVIF encoding, use external tools (squoosh.app, avif.io, or the avifenc CLI).

Question 8

Does this strip EXIF metadata?

Accepted Answer

Yes. The Canvas API does not preserve EXIF when re-encoding — the resulting file contains only pixel data and the minimal metadata the output format requires (no camera make/model, GPS coordinates, timestamps, or any custom tags). This is a privacy benefit when sharing photos online, but if you need to preserve EXIF (for digital-asset-management systems that index by camera), compress with a tool that supports metadata pass-through (mozjpeg --copy-all, ImageMagick with -strip removed).

Question 9

Is my image sent to any server?

Accepted Answer

No. The entire pipeline (read → decode → re-encode → download) runs in your browser tab via the Canvas API and Blob URLs. There are no fetch requests carrying image data, no analytics events with file bytes, no cookies set with image identifiers. The image exists only in the current tab's memory and is cleared on refresh. Sensitive imagery (medical, personal, internal documents) can be compressed here without privacy concern.

Format	Best For	Transparency	Lossless	Typical Size
JPEG	Photographs, complex gradients, real-world imagery	No	No	Baseline (1.0×)
WebP (lossy)	Modern websites — replaces JPEG for photos and PNG for graphics	Yes (alpha)	Yes (separate mode)	~0.70× of JPEG at same visual quality
AVIF	Next-gen photo compression; supported in modern browsers	Yes (alpha)	Yes	~0.50× of JPEG; slower to encode
PNG	Screenshots, logos, line art, images needing transparency	Yes (alpha)	Always lossless	5-10× of JPEG for photographs

Quality Range	Visual Impact & Best Use
95-100	Nearly indistinguishable from source. Use when you cannot afford any visible artefacts.
85-94	Default for high-quality web photos. Artefacts only visible in side-by-side comparison.
70-84	Web standard for body images. Some artefacts visible in solid color areas; usually invisible at normal viewing.
50-69	Thumbnails, hero backgrounds, low-stakes images. Compression artefacts become noticeable.
0-49	Aggressive — use only for very small thumbnails or when bandwidth is critical. Artefacts are obvious.

Free Image Compressor: Reduce JPG, PNG & WebP File Size in Your Browser

Quality + Downscale

JPEG, WebP, PNG

Live Before/After

100% Client-Side

Reduce Image Size Without Uploading Anywhere

Image Format Comparison (2026)

How to Pick the Right Quality Level

Web Image Optimisation Best Practices

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