Math CAPTCHA for WordPress Comments: Does It Still Stop Spam? (2026)
Can a simple sum like “3 + 4 = ?” really stop spam? A math CAPTCHA for WordPress comments asks visitors to solve an easy arithmetic question before their comment is accepted. Back in 2007 it worked remarkably well for us. Here is what happened, why we eventually removed it, and whether a math question is still a good anti-spam choice in 2026.
Quick answer: A math CAPTCHA blocks simple spam bots that can’t read or answer the question, and it is easier on humans than distorted-text CAPTCHAs. But modern bots can often solve basic sums, and buggy plugins can reject correct answers. In 2026 most blogs do better with a spam filter (Akismet or Antispam Bee) plus an invisible honeypot or Cloudflare Turnstile. A math question is still a reasonable extra layer on small sites.
Table of Contents
Our 2007 math CAPTCHA experiment
In December 2007, Akismet was blocking over 2,000 spam comments a day on QuickOnlineTips, yet a few still slipped through to moderation. We installed the Math Comment Spam Protection plugin, which added a simple sum to the comment form. The results were dramatic:
- Spam waiting for moderation dropped to almost zero.
- Akismet-caught spam fell from about 2,000 a day to about 100 a day, because most bots never got past the question.
- Checking the spam folder became possible again. Before, we simply deleted all 2,000 daily spam comments, since finding the one genuine comment among them was impossible.
- Database backups started working again. The huge volume of stored spam had made our backup emails fail; with less spam, backups shrank and arrived reliably.
Setup in those days meant uploading the plugin by FTP and pasting a snippet of code into the theme’s comments.php file. A math question on our contact form had a similar effect: contact form spam stopped from the day we added it.
Why we stopped using it
Some time later we removed the plugin. Several readers reported that even when they entered the correct total, the plugin insisted the answer was wrong. Losing genuine comments is worse than moderating spam, so the plugin had to go. That old plugin has long since disappeared, and its original homepage is no longer available.
Does a math CAPTCHA for WordPress comments still work in 2026?
Pros:
- Easy for most people: no squinting at distorted text or picking traffic lights.
- Blocks basic, untargeted bots that fill in every field blindly.
- Works without third-party services or tracking.
Cons:
- Smarter bots can parse and solve simple sums.
- Adds friction, and can be a barrier for some users, including those using screen readers if not implemented accessibly.
- Broken or caching-incompatible plugins can reject correct answers, as we learned the hard way.
Better ways to stop WordPress comment spam today
- Akismet (external site) or Antispam Bee (external site): filter spam automatically after submission.
- WP Armour (external site): an invisible honeypot field that bots fill in and humans never see. No puzzle at all.
- Simple CAPTCHA with Cloudflare Turnstile (external site): a free, privacy-friendly challenge that most visitors pass without solving anything.
- Captcha by BestWebSoft (external site): if you still want a math question, its free version includes arithmetic CAPTCHAs (addition, subtraction, multiplication) for comments and forms.
Whatever you choose, test it yourself after installing, including with your caching plugin active, and occasionally check that real comments are getting through.
See our full comparison of the best WordPress plugins to stop comment spam, read what we learned from 3 million blocked spam comments, and learn how to remove links in WordPress comments to cut the incentive for spammers.
FAQ
What is a math CAPTCHA?
A challenge that asks users to solve a simple arithmetic problem, such as 5 + 3, before submitting a form, to prove they are human.
Can bots solve math CAPTCHAs?
Many simple bots can’t, but more advanced bots can read and solve basic sums, so a math question alone is not strong protection.
Is a math CAPTCHA better than reCAPTCHA?
It is simpler and doesn’t rely on a third party, but it is weaker against determined bots. Invisible options like honeypots or Cloudflare Turnstile offer a better balance for most blogs.
Do CAPTCHAs reduce genuine comments?
Any extra step can discourage some commenters, and buggy implementations can block them entirely. Prefer invisible protection where possible.
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Great list. I would add Comment E-Mail Verification to the ones that protect you from spam.
Thanks
Unless you want to try an illegible and barely visible captcha, the plugin is highly recommended. After the usual installation via FTP and activation via the plugin admin area, you need to paste a strip of code in your comments.php to integrate the math question. The code works well if your comments template is based on the default comments.php file. It worked fine on my template and works great. Try it.
This is a very useful post, I was looking for this info. Just so you know I discovered your website when I was browsing for blogs like mine, so please check out my site sometime and leave me a comment to let me know what you think.
I don’t agree with everything in this post, but you do make some very good points. Im very interested in this matter and I myself do alot of research as well. Either way it was a well thoughtout and nice read so I figured I would leave you a comment. Feel free to check out my website sometime and let me know what you think.
Unless you want to try an illegible and barely visible captcha, the plugin is highly recommended. After the usual installation via FTP and activation via the plugin admin area, you need to paste a strip of code in your comments.php to integrate the math question. The code works well if your comments template is based on the default comments.php file. It worked fine on my template and works great. Try it.
I’ve been looking for something like this. Hopefully it will do the trick
I might just have to try this.
spam captcha installed on my blog but I found out that it http://www.wowgoldsell.com caused conflict with incoming trackbacks. I know it
I might just have to try this. Thanks!
I have stopped using this plugin since several readers reported that although the total was right, the plugin kept persisting the total was wrong.
I might just have to try this. Thanks!
a really great and useful tool, thanks for it
I might just have to try this. Thanks! Indeed, works perfectly combined with akismet.
It is really working well for me with Akismet. Now I waste less time filtering spam.
a really great and useful tool, thanks for it
a really great and useful tool, thanks for it
I am not bothered with comments spam because Akismet has been doing very good work for me. However I am bothered about spam trackbacks.
But I guess Akismet has started to block those too recently.
I once had this type of spam captcha installed on my blog but I found out that it caused conflict with incoming trackbacks. I know it was caused by the plugin because after I uninstalled it, the issue was resolved.I might just have to try this. Thanks!
Sum of 6 + 7 ? is an arithmetic question not a math question. a common mistake.
It is really working well for me with Akismet. Now I waste less time filtering spam.
Indeed, works perfectly combined with akismet.
I might just have to try this. Thanks!
I once had this type of spam captcha installed on my blog but I found out that it caused conflict with incoming trackbacks. I know it was caused by the plugin because after I uninstalled it, the issue was resolved.