Who needs images under 150KB?
Bloggers and site owners often aim for images in this range so pages load quickly on mobile connections. Email newsletters benefit too, since every image adds to the size of the email. Some upload forms also set their limit at 150 KB for photos or documents.
A photo of about 1200 by 800 pixels usually fits at a quality where compression is hard to spot.
Sizing images for blogs and newsletters
Size the image for where it will be shown. Email layouts are commonly around 600 pixels wide, and an image at twice that width, about 1200 pixels, stays sharp on high-density phone screens. Blog content columns are often 700 to 900 pixels wide, so the same 1200-pixel image works there too.
Resize first, then compress. An image already at its display size leaves more of the 150 KB for detail, so the tool can use a higher quality.
How to compress to 150KB
Upload the image. The 150 KB target is set automatically. Pick JPG for maximum compatibility, or WebP for your own website where it usually stores more detail in the same size. PNG uploads start as JPG. If you choose PNG output, the target no longer applies, because PNG is lossless.
The tool finds the highest quality under 150 KB and shows the new size and dimensions next to the original. If the dimensions changed, the status line says so.
When to choose a different target
If the image is a small thumbnail or avatar, 50 KB is plenty and keeps pages with many images light. If it is a full-width banner or a photo people will zoom into, 500 KB gives room for more pixels. For a document upload with a 150 KB cap, crop the page to its edges first and make sure the smallest text is still readable in the preview before you submit it.