Histogram
Red, green and blue channel histograms.
This runs in your browser. Nothing is uploaded.
About Histogram
Counts how many pixels sit at each of the 256 levels in the red, green and blue channels, draws the three curves into the preview and reports each channel's peak, in your browser.
Judging exposure by eye is unreliable and you already know it. A phone screen in daylight hides blown highlights, a laptop at forty percent brightness makes everything look crushed, and a cheap monitor lies in both directions. A histogram is the measurement underneath the impression: it says what is actually in the file rather than what your display is doing to it.
Every pixel is tallied into three arrays of 256 bins, one per channel, and the result is drawn as three traces on a 512 by 200 chart scaled so the tallest bin anywhere touches the top. Dark is on the left, bright on the right. A wall against the right edge means clipped highlights; a wall on the left means blocked shadows; everything bunched centrally means a flat, low-contrast image.
The printed peak values are the most common level in each channel, which is not the average and not the maximum. A photo with a big plain sky will report the sky's blue and tell you little about the subject. The chart also replaces the image in the preview pane while you read it, there is no download for it, and there is no combined luminance trace — only the three colour channels.
How to use Histogram
- 1Drop the image onto the panel.
- 2Click Analyze.
- 3Read the three traces in the preview, dark on the left and bright on the right, plus the peak values printed below.
What it won't do
- Red, green and blue only, with no luminance or combined curve.
- The chart takes over the preview, so you cannot see the image and the histogram together.
- No numbers beyond the per-channel peaks, and no download for the chart.
Common questions
How do I read an image histogram?
Left is dark, right is bright, and the height of the curve is how many pixels sit at that level. A spike jammed against the right edge means highlights that have clipped to white and hold no recoverable detail; a spike at the far left means shadows crushed to black. Most well-exposed photos spread across the range without piling up at either end.
What do the R, G and B peak numbers mean?
Each one is the single most common level in that channel, on a scale of 0 to 255. If the three peaks land close together the image is roughly neutral at its most common tone; a wide gap between them points to a colour cast, which the white balance and levels tools can pull back.
Does this include a luminance histogram?
No, only the three colour channels drawn separately. There is no combined brightness or RGB-average trace, so read overall exposure from where all three curves sit together rather than looking for a single grey curve. For most exposure decisions the three traces tell you the same story.
Can I save the histogram as an image?
Not from this panel — the chart is drawn into the preview and there is no download for it. A screenshot is the practical answer if you need to keep or share it. The image itself is untouched; nothing about running the analysis changes the file you loaded.
Related tools
Why this one doesn't upload your file
There is no server to upload to. This page is a static file, and the work happens in your browser using the same graphics and WebAssembly code that renders every other site you visit. Your file is read from disk into memory, processed, and handed back as a download. Once the page has loaded you can disconnect from the network entirely and it keeps working. The longer explanation