Are my images uploaded?

No. The file is read by your browser, redrawn to a canvas and re-encoded locally. No network request carries your image, which you can verify in the network tab of your developer tools. This is the main reason to use a browser-based compressor for anything sensitive.

Which formats are supported?

JPEG, PNG and WebP as output. Choose JPEG for photographs, PNG for screenshots and anything needing transparency or flat colour, and WebP when you want the best compression and your audience is on current browsers.

Why does the quality slider do nothing for PNG?

Because PNG compression is lossless: it reproduces every pixel exactly and has no quality dial to turn. To make a PNG smaller you either reduce its dimensions or convert it to a lossy format. The tool says so rather than leaving the control apparently broken.

Should I resize or compress?

Resize first. Dimensions dominate file size, and an image displayed at eight hundred pixels wide gains nothing from being four thousand. Scale to about twice the largest display size, to cover high density screens, and then adjust quality.

What does the aspect ratio lock do?

Keeps width and height proportional, so changing one adjusts the other. Unlock it only when you genuinely want to distort the image, which is rare; if you need a different shape, crop rather than stretch.

Is WebP safe to use now?

Yes. Every current browser supports it, including Safari since 2020. If you need to support genuinely old browsers, serve WebP with a JPEG or PNG fallback using the picture element, which degrades cleanly.

Does compression remove EXIF data?

Re-encoding through a canvas discards the metadata, including GPS coordinates and camera details. That is usually welcome, since location data in a published photograph is a real privacy problem. It also means a deliberately preserved copyright field will not survive, so keep the original if the metadata matters.

Can I compress an image more than once?

You can, and you should avoid it. Lossy compression discards information permanently, and the loss accumulates with each pass, which is why heavily edited images look soft. Always start from the highest quality original available.

Is there a file size limit?

No fixed limit, but very large images are held in memory and drawn to a canvas, so an extremely large file may be slow or exhaust memory on a modest device. For images of ordinary photographic size, performance is not an issue.

Image Optimizer – Compress and Resize Without Uploading

Image Optimizer

🖼️Drag and drop an image, or click to choose onePNG, JPEG, GIF, WebP

// Image Optimizer: Features

Nothing is uploaded, which is the point

Almost every online image compressor sends your file to a server, processes it there and sends it back. For a stock photo that is fine; for a screenshot containing customer data, an unreleased product image or a document photographed for a client, it means handing the file to a third party. Here the file is read by your browser, redrawn to a canvas and re-encoded locally. It never leaves your machine, which you can confirm in the network tab.

Choosing a format

JPEG suits photographs, where its lossy compression is efficient and its lack of transparency rarely matters. PNG is lossless and the right choice for screenshots, diagrams and anything with flat colour or transparency, at the cost of size. WebP usually beats both, often by a substantial margin at equivalent quality, and supports transparency; browser support is universal among current versions. Converting a photographic PNG to WebP or JPEG is frequently the single largest saving available.

Resizing is usually the bigger win

Quality settings get the attention, but dimensions dominate file size: halving both width and height quarters the pixel count. A photograph straight from a phone can be four thousand pixels wide and displayed at eight hundred, which means most of the data is discarded by the browser after being downloaded. Resizing to roughly twice the largest display size, to cover high density screens, before touching quality is the right order of operations.

What the quality setting does

For JPEG and WebP, quality controls how aggressively detail is discarded. Values between seventy-five and eighty-five are the usual sweet spot: visually indistinguishable from the original for most photographs while cutting size considerably. Below about sixty, artefacts become visible in smooth gradients and around sharp edges. PNG is lossless, so the quality setting has no effect there, which the tool states rather than letting you wonder.

Compression is one-way

Re-encoding a lossy image always loses information, and the loss accumulates. Compressing an already-compressed JPEG a second time degrades it further even at high quality, which is why images that have been through several rounds of editing and saving look soft. Always work from the highest quality original you have rather than from a copy that has already been optimised.

// Image Optimizer: FAQ

Are my images uploaded?: No. The file is read by your browser, redrawn to a canvas and re-encoded locally. No network request carries your image, which you can verify in the network tab of your developer tools. This is the main reason to use a browser-based compressor for anything sensitive.
Which formats are supported?: JPEG, PNG and WebP as output. Choose JPEG for photographs, PNG for screenshots and anything needing transparency or flat colour, and WebP when you want the best compression and your audience is on current browsers.
What quality setting should I use?: Between seventy-five and eighty-five for JPEG and WebP. That range is visually indistinguishable from the original for most photographs while cutting the file size substantially. Below sixty, artefacts become visible in gradients and around edges.
Why does the quality slider do nothing for PNG?: Because PNG compression is lossless: it reproduces every pixel exactly and has no quality dial to turn. To make a PNG smaller you either reduce its dimensions or convert it to a lossy format. The tool says so rather than leaving the control apparently broken.
Should I resize or compress?: Resize first. Dimensions dominate file size, and an image displayed at eight hundred pixels wide gains nothing from being four thousand. Scale to about twice the largest display size, to cover high density screens, and then adjust quality.
What does the aspect ratio lock do?: Keeps width and height proportional, so changing one adjusts the other. Unlock it only when you genuinely want to distort the image, which is rare; if you need a different shape, crop rather than stretch.
Is WebP safe to use now?: Yes. Every current browser supports it, including Safari since 2020. If you need to support genuinely old browsers, serve WebP with a JPEG or PNG fallback using the picture element, which degrades cleanly.
Does compression remove EXIF data?: Re-encoding through a canvas discards the metadata, including GPS coordinates and camera details. That is usually welcome, since location data in a published photograph is a real privacy problem. It also means a deliberately preserved copyright field will not survive, so keep the original if the metadata matters.
Can I compress an image more than once?: You can, and you should avoid it. Lossy compression discards information permanently, and the loss accumulates with each pass, which is why heavily edited images look soft. Always start from the highest quality original available.
Is there a file size limit?: No fixed limit, but very large images are held in memory and drawn to a canvas, so an extremely large file may be slow or exhaust memory on a modest device. For images of ordinary photographic size, performance is not an issue.

// How to Use Image Optimizer

Drop in an image to compress

Drag a file onto the drop area or click to choose one. The original dimensions and file size are shown so you have a baseline to compare against.
Resize first, then set quality

Reduce the dimensions to about twice the largest size the image will be displayed at, keeping the aspect ratio locked. Then choose the output format and adjust quality, usually to between seventy-five and eighty-five.
Check the saving and download

The comparison shows the original size, the new size and the reduction. Confirm the result still looks right at full size before downloading and replacing the original.

Category Design