Why copy that code?

For each calculation, you are kindly asked to enter a captcha code as it is shown in this image. The reason is: we can give away free calculations with guaranteed correctness only to real humans. Therefore, we need to verify that you are a human and not a computer. This website has been inundated with requests for calculations from remote servers instead of people, which caused a high load. By forcing this captcha on you, we make sure we can keep offering you this free service.

If you find the captcha really annoying, please consider using the ad-free and captcha-free professional version.

Hard to read?

Here are a few hints in case the text is illegible:

• We only use numbers and lower-case letters. In the example above, even though it vaguely looks like there is a capital A, that can't be it because of the "only lower-case letter" rule. So in this case, the code must be: d74e
• We always use either 4 or 5 characters.
• The code does not change very quickly. If it happens to be rendered badly, simply reload the page to create a - hopefully - better rendition of the same code.