How to Compress an Image Without Visibly Losing Quality

Modern phone cameras take beautiful pictures, and they produce large files. That is a problem when a form refuses anything above two megabytes, when an email bounces because of its attachments, or when a web page takes forever to load because it is carrying oversized photos. Compression solves all of these, and when it is done sensibly the difference is almost invisible.

What compression actually does

Two settings determine the size of an image file: its dimensions in pixels, and the quality used when it is encoded. A photo of 4000 by 3000 pixels contains twelve million pixels, far more than a screen needs to display it. Reducing the dimensions and choosing a sensible quality can shrink the file dramatically, because you are removing detail that nobody would have seen anyway.

Choose the right format

• JPEG is the best choice for photographs. It gives a much lighter file by discarding detail the eye barely notices.
• PNG is lossless, which means it keeps every pixel exactly. It is better for screenshots, logos, and images with text or sharp edges, but the files are heavier.
• WEBP files can be added as input to the tool and converted to a format you can use everywhere.

How to compress an image step by step

1. Open the Compress Image tool.
2. Add your image in JPG, PNG, or WEBP format.
3. Choose the output format: JPEG for a lighter file, or PNG to stay lossless.
4. Adjust the JPEG quality and, if needed, the pixel dimensions. The aspect ratio can be locked so that the picture is not distorted.
5. Click Compress, compare the original size with the new size, and download the result.

Everything happens in your browser, so your photos are not uploaded to a server.

Finding the right quality setting

For everyday web use, a JPEG quality of around 70 to 80 percent is a good trade-off: the file is much lighter, and the difference is nearly invisible to the eye. Below roughly 50 percent, artifacts such as blocky areas and blurred edges start to become visible. If the image will be printed or examined closely, stay higher. The best approach is to try a setting, compare the preview against the original, and adjust.

Resize before you compress

Often the biggest gain comes from reducing the dimensions. A picture displayed in a column 800 pixels wide does not need to be 4000 pixels wide. Resizing it to something close to the size at which it will actually be shown cuts the file size sharply. As a rule, aim for dimensions slightly larger than the largest size at which the image will appear, to keep it sharp on high-resolution screens.

Typical targets

• Website images: smaller files load faster and improve the experience for visitors on mobile connections.
• Online forms: to meet a strict upload limit for an ID photo or a document, reduce quality gradually until you fall below the limit, rather than going straight to a very low setting.
• Email attachments: compress several photos so that they all fit under your provider's size cap.

Keep your original

Compression is not reversible: once detail has been discarded, it cannot be recovered. Always keep the original file, and save the compressed copy under a new name, for example by adding -small to the filename.

Working with documents

If your goal is to send several photos as one document, you can turn them into a PDF with the JPG/PNG to PDF tool. See our guide on how to turn photos into a PDF for tips on layout. For PDF files that are too large, the Compress PDF tool does the same job for documents.

Frequently asked questions

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