Image Format Converter

Converting between JPEG, PNG and WebP is usually a two-minute job that turns into a twenty-minute one, because the obvious route is an upload site you do not want to send a client's artwork to. The converter above does it in the browser: pick files, pick a format, download.

How it works

Drop in up to 20 JPEG, PNG or WebP images at once. Choose the output format and, for the lossy formats, a quality level; each file is re-encoded and listed with its size before conversion and its new size after, so you can see what the conversion bought you.

Under the hood each image is decoded to a bitmap, drawn onto a canvas at its original dimensions — this is a format change, not a resize — and re-encoded. Two details in that pipeline are worth knowing:

• EXIF orientation is applied. A photo shot in portrait on a phone is stored with a rotation flag rather than rotated pixels. The converter honours that flag, so the output is the right way up rather than the way the sensor saw it.
• Transparency gets a white matte when the target is JPEG. JPEG has no alpha channel. Without a matte, transparent pixels from a PNG or WebP source encode as black, which is the classic "why is my logo on a black box" result. The canvas is filled white first.

PNG output ignores the quality slider, because the canvas encoder always writes PNG losslessly. SVG input is not accepted: it is vector, and rasterising it needs a target size the tool has no way to guess.

Everything runs locally. No file is uploaded, nothing is stored, and the tool works with the network disconnected.

Choosing a format

WebP is the sensible default for the web. At equivalent perceived quality it is typically 25–35% smaller than JPEG, it supports transparency and animation, and it has been supported by every current browser for years. Use it unless something downstream cannot read it.

JPEG remains the safest interchange format: every tool, every printer, every decade-old system reads it. It has no transparency and it is lossy, so each re-encode degrades the image slightly.

PNG is lossless and supports transparency, which makes it right for logos, icons, diagrams and screenshots of text — anything with hard edges and flat colour, where JPEG's blocking artefacts are most visible. It is a poor choice for photographs, where it can be several times larger than a JPEG nobody would tell apart.

The one rule that matters: do not convert lossy to lossy without reason. JPEG → WebP → JPEG loses quality at each step and cannot recover it. Convert once, from the best source you have.

Quality settings

For WebP and JPEG, quality 0.8–0.9 is usually indistinguishable from the original at normal viewing size while saving a large fraction of the bytes. Below about 0.7, artefacts appear around sharp edges and text first. Do not treat the slider as a size target: the same setting produces very different sizes depending on how much detail the image contains.

Converting an already-compressed JPEG at quality 1.0 makes the file larger without adding any information back. If size is the goal rather than format, the image compressor is the more direct tool.

Where this fits

Image weight is usually the largest single contributor to how slow a page feels, and format choice is the cheapest lever available — before caching, before a CDN, before code splitting. Application performance covers measuring what actually delays a page, and HTML5 essentials covers <picture> and srcset, which let you ship WebP with a JPEG fallback and the right size for each viewport.

Related tools

To change dimensions rather than format, use the image resizer; to cut a region out, the image cropper; to reduce file size at the same format, the image compressor.