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DevBench

How do I watermark an image online?

  1. Upload a PNG, JPEG or WebP photo — it is decoded locally and never uploaded.
  2. Type the watermark text, then set font size (in pixels at full resolution), colour with its own alpha slider, overall opacity, and rotation.
  3. Pick a layout: Tile (diagonal) repeats the text across the whole picture, or Single places one stamp using the nine-position grid — centre, corners, edges.
  4. Choose PNG, JPEG or WebP output (quality slider for the lossy two) and download.

How do I keep a watermark readable?

Busy photos swallow flat text. Turn on the outline-and-shadow toggle: it strokes each letter with the contrasting colour — white over dark text, near-black over bright text — and adds a soft shadow, so the credit stays legible without cranking opacity. For subtle watermarks, leave colour alpha at full and dial the overall opacity down instead; for deterrents, tile at higher opacity so the image cannot simply be cropped free of the mark.

What are the limits?

Input images are capped at 16,384px per side and roughly 50 megapixels, the same safe canvas limits as the other image tools. The preview is capped at 1,000px on its longest side so slider changes stay smooth — downloads always render at your image's original dimensions. PNG and WebP keep transparency; JPEG has none, so transparent areas composite onto white. Text is the only watermark type: there is no image or logo stamp here. Everything runs 100% in your browser.

Also useful: Image Compressor.