Image Similarity

Upload two images to calculate pixel-level similarity, mean squared error (MSE), and peak signal-to-noise ratio (PSNR), with an adjustable tolerance threshold.

Image A

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Image B

Drop an image or click to upload

What Is Image Similarity?

Image similarity compares the color differences of two images pixel by pixel and reports objective metrics such as similarity percentage, MSE, and PSNR.

It's commonly used to measure quality loss after compression, detect whether an image has been modified, or find duplicate images.

How to Use

Compare similarity in three steps:

  • Upload Image A and Image B.
  • Adjust the tolerance threshold.
  • Click Compare to view similarity, MSE, and PSNR.

Tips

  • A PSNR above 30 dB usually means very little quality loss.
  • The default tolerance is 10 — keep it as is, then fine-tune if needed.
  • Pair this with the Perceptual Image Hash tool to compare images that are similar in content but different in size.

Frequently Asked Questions

How is similarity calculated?+
The RGB values are compared pixel by pixel. Two pixels are considered similar when their color difference is within the tolerance, and the similarity percentage is the proportion of similar pixels.
What do MSE and PSNR mean?+
MSE (mean squared error) is smaller when the two images are closer. PSNR (peak signal-to-noise ratio) is measured in dB — above 30 dB generally indicates near-lossless quality.
What happens if I increase the tolerance?+
A larger tolerance treats pixels with small color differences as similar, so similarity increases. A smaller tolerance makes the comparison stricter.
Can images of different sizes be compared?+
Yes. The tool scales both images to the same size before comparing them pixel by pixel.

Related Tools

Image CompareDuplicate Image FinderPerceptual Image Hash

Image Similarity — free online image similarity, image comparison, mse, psnr, image similarity calculator. No signup required. Works in your browser.