Brightness / contrast is a free tool that runs entirely in your browser. Lighten or darken and boost contrast. It takes care of a common image chore in a single click, right inside your browser. Because everything happens locally with pdf-lib and pdf.js, your files are never uploaded to a server — Brightness / contrast works instantly, even offline, and keeps every document completely private, with no account, no watermarks and no file-size limits.
How to use Brightness / contrast
- 1Open the Brightness / contrast tool and drop in your images, or click to choose it.
- 2Set your options — Brightness %, Contrast % — then press Run.
- 3Download your result. The whole thing happens on your device, so your images never leave your browser.
100% private — nothing is uploaded
Unlike most online PDF tools, Brightness / contrast never sends your images to a server. Everything is computed locally in your browser with JavaScript, so your documents stay on your device. There's no account, no watermark and no file-size limit — and it even keeps working with your Wi-Fi switched off.