Compress JPG

The quality number is not a percentage of anything. It is an index into how aggressively detail is discarded, and the useful range is narrower than people expect:

• 90–95 — Barely smaller than the original for a file that has already been compressed once. Rarely worth it here.
• 75–89 — The sensible band. 75 is the default and typically halves the size of a camera JPG with no difference visible at normal viewing distance.
• 55–74 — Clearly smaller. Fine for web images and email; look closely at any faces or fine detail before committing.
• Below 55 — Blocking and colour banding become obvious, especially in skies and shadows. Use only when a hard size limit leaves no choice.

If the file barely shrinks, it was probably already compressed hard — there is little left to remove. Lower the quality further, or reduce the dimensions instead with the resize tool, which is usually the more effective lever: halving the width and height cuts the pixel count to a quarter.

If the file grows, you have asked for a higher quality than the original was saved at. Nothing is gained — the discarded detail cannot come back — so keep the original.

When compressing is the right tool

• Upload limits. Job portals, government forms, marketplaces and older content systems frequently cap uploads at 1–2 MB, which a modern phone photo exceeds easily.
• Email attachments. A handful of camera photos will exceed most mailbox limits; compressed, the same set fits comfortably.
• Website performance. Images are the largest part of most pages, and page speed affects both search ranking and how many visitors stay.
• Storage and backups. A large library compresses to a fraction of its size with no visible difference.

When to reach for something else

If your goal is a smaller file for a website, converting to WebP usually beats compressing the JPG: WebP is a more efficient format, so you get a smaller file at the same visible quality rather than trading quality for size.

If the image is much larger than it needs to be on screen — a 4000px photo displayed at 800px — resizing is the better first move. It reduces file size far more than compression does, and unlike compression it costs no visible quality at the size it is actually viewed.

And if the image is a screenshot, a diagram or anything containing text, JPEG is the wrong format entirely. Compressing it will smear exactly the edges that make it readable. WebP handles that kind of image far better.

Hitting a specific file size

If a form demands "under 500 KB", work down rather than guessing: start at 75, check the size shown next to each file, and step down in fives. Each attempt takes a few seconds, so trying several settings is quick.

When quality alone cannot get you there, reduce the dimensions as well. A photo at half the width and height has a quarter of the pixels, which almost always achieves more than pushing the quality slider into the range where the image visibly falls apart.

What happens to camera metadata

EXIF data — camera model, exposure, timestamps and often GPS coordinates showing exactly where the photo was taken — is not carried into the compressed file. That is usually what you want when posting photographs publicly.

The orientation flag is applied to the pixels before it is discarded, so a photo taken on a phone stays the right way up rather than appearing on its side.