Add punch to a flat photo or soften a harsh one. One slider from 0 to 200 percent, live preview, and the file never leaves your device.
Stretches or squeezes every tone around mid-grey. Above 100 percent, pixels darker than 128 get darker and pixels lighter than 128 get lighter, so the picture gains separation between shadows and highlights. Below 100 they are pulled towards grey and the image flattens. It uses the same curve as desktop editors, so 125 here matches roughly +25 in those tools. Mid-grey itself does not move, which is why contrast alone never makes a picture look brighter or darker overall.
A landscape shot through haze has its darkest pixel at 60 and its brightest at 190, a span of 130 out of a possible 255. At 140% contrast the darkest becomes 33 and the brightest 215, a span of 182, and the hills that were grey-on-grey separate into distinct layers. At 200% the span reaches the full 0 to 255 but the smooth sky starts to show bands. A 1600 × 1200 JPEG re-saved at quality 92 after this change comes out about 5 to 10 percent larger, because there is more edge detail to encode.
Use it for low-contrast sources: photos through glass or fog, scans of faded prints, screenshots with pale text, product shots on white that look washed out. It also rescues images that were brightened too far and now look milky. Do not use it on portraits at high values, since it deepens shadows under eyes and exaggerates skin texture; 110 to 120 is plenty there. If the picture already has deep blacks and bright whites, more contrast only destroys detail at both ends, and what you may actually want is Change Saturation for stronger colour or Sharpen Image for crisper edges.
Contrast runs from 0, a uniform grey card, through 100, the original, to 200, the strongest stretch. The chips cover the useful range. Values under 100 are a legitimate tool for softening harsh flash photos or making a background image quieter behind text. The Output section picks the file type and JPEG quality; use Same to keep what you dropped. Batch mode applies one setting to a whole folder.
Why does the sky look banded at high contrast? Stretching a smooth gradient spreads its 256 possible values further apart, so steps that were invisible become visible bands. Stay under about 150 percent on images with large smooth areas, or add a little Add Noise afterwards to dither the bands.
Does contrast change the brightness? Not the average. Mid-grey stays at 128; tones above it go up and tones below it go down by the same proportion. If the picture looks darker afterwards it is because the shadows caught your eye, not because the mean shifted.
Which should I do first, brightness or contrast? Contrast first, then brightness, so the brightness shift is not amplified by the contrast curve. Brightness & Contrast applies them in that order for you in one pass.
Is my photo uploaded? No. Everything runs in the browser tab. You can turn the network off after the page loads and it still works.