Image Resizer

Upload forms very often reject a photo purely because the file is too heavy. Rather than guessing at the quality slider, switch to the File size tab and type the limit you have been given — 20 KB, 50 KB, 100 KB or anything else.

The tool then searches for the highest JPEG quality that still fits under your target, keeping the full pixel dimensions wherever possible. Only if your target cannot be reached at the lowest usable quality will it start reducing dimensions as well, so you always keep as much detail as the limit allows. A 4 MB phone photo can be brought under 100 KB in a couple of seconds without leaving the page.

The same works in reverse for generous limits: if a form allows up to 10 MB you can keep near-original quality and simply convert the format.

For an online passport application through GOV.UK, the digital photo must be at least 600 pixels wide and 750 pixels tall, and the file must be at least 50 KB and no more than 10 MB. Both the minimum and the maximum matter: an over-compressed photo below 50 KB is rejected just as readily as one over 10 MB.

Use the “UK passport photo (online application)” preset to hit 600 × 750 exactly, then check the resulting file size shown next to the image. If it lands under 50 KB — which can happen with a plain background — raise the quality slider until it comfortably clears the minimum.

Printed photos are the traditional 35 × 45 mm. The print preset renders at 300 dpi and stamps the correct print density into the file, so a photo lab or home printer reproduces it at the right physical size rather than treating it as a 72 dpi screen image.

• JPG is right for photographs and for almost every official upload. It compresses smoothly, and it is the format government and job portals expect. It cannot store transparency, so any transparent area is filled with your chosen background colour.
• PNG is lossless and keeps transparency, which makes it the choice for logos, screenshots and graphics with sharp edges or text. Photographs saved as PNG are typically several times larger than the same image as JPG.
• WebP gives noticeably smaller files than JPG at the same visual quality and is ideal for your own website. Some older software and a few upload forms still will not accept it, so avoid it for official submissions.

Converting between them here is one click — pick the format before you press resize. Quality between about 75 and 85 is usually indistinguishable from the original while cutting file size dramatically.

eBay UK requires the longest side of a listing photo to be at least 500 px, and recommends 1600 px so buyers can zoom. Vinted and Facebook Marketplace both re-compress what you send, so uploading a 1200–1600 px image gives a sharper result than a full-resolution phone photo that gets crushed on their servers.

For email, keeping attachments under about 10 MB in total avoids most corporate mail filters — resizing a batch of holiday photos to 1600 px wide usually takes a 40 MB set down to under 5 MB. Use the bulk mode and download everything as one ZIP.