by RicheyWeb 1 (0 reviews)

HashCash - Proof of Work CAPTCHA

Name: HashCash - Proof of Work CAPTCHA
Author: RicheyWeb

Invisible Proof-of-Work CAPTCHA. No checkboxes, no image grids, no Google, no tracking. Just spam protection that gets out of the way.

HashCash ranks #57,965 among WordPress.org plugins with 1+ active installations, is #2,192 of 2,900 in the Discussion & Community category, a 1/5 rating from 0 reviews, and was last updated Jun 15, 2026. Data from WordPress.org, refreshed twice daily — see methodology.

Tested up to WP 7 (Current: 7.1.2)

v1.0.10 Current Version v1.0.10

Updated 3 months ago Last Update on 15 Jun, 2026

Refreshed 20 hours ago Last Refreshed on

#2,192 of 2,900 in Discussion & Community

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Rank

#57,965

— No change

Active Installs

— No change

KW Avg Position

138

9 worse

Downloads

179

+1 today

Support Resolved

— No change

Rating

20%

Review 1 out of 5

1 (0 reviews)

Next Milestone 10

Total Progress 20%

0+ 10+

45,028

Ranks to Climb

Growth Needed

8,000,000

Active Installs

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Rank Changes

Current #57,965

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Active Installs Growth

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Active Installs 0,000,000+

Growth +0.0%

Peak 0,000,000

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Reviews & Ratings

1.0

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Overall 20%

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Plugin Details

Version: 1.0.10
Last Updated: Jun 15, 2026
Requires WP: 6.0+
Tested Up To: 7
PHP Version: 7.4 or higher
Author: RicheyWeb

Support & Rating

Rating: ★ ☆ ☆ ☆ ☆ 1
Reviews: 0
Support Threads: 0
Resolved: 0%

Keywords

Proof of Work anti-spam antispam captcha contact form 7

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Frequently Asked Questions

Common questions about HashCash - Proof of Work CAPTCHA

Yes. HashCash requires no third-party service, no API key, and sends no data to external servers. If you're using reCAPTCHA or hCaptcha specifically to avoid tracking your users, HashCash is a direct replacement.

While the proof-of-work calculation runs, a brief "Securing this form..." message appears and the submit button is temporarily disabled. When the calculation completes — usually within seconds at default settings — the button re-enables and the indicator disappears. There is nothing for the user to click, solve, or interact with.

No. Logged-in users are exempt from HashCash verification entirely.

No. The proof-of-work calculation runs in a Web Worker (a background browser thread) and only starts when the user interacts with the form. Your page load time is not affected.

Argon2id is the current gold standard for memory-hard cryptographic hashing — it's specifically designed to be expensive for bots running at scale while remaining fast enough for individual users. It requires the PHP sodium extension (available by default in PHP 7.2+). If your server supports it, it's the strongest option available. SHA-256 remains the default for maximum compatibility.

When suspicious behavior is detected (automated form submission patterns, headless browsers, CDP runtime signatures), HashCash can either silently fail or make the proof-of-work impossible to solve. Punishment mode chooses the latter — the bot wastes significant compute resources without knowing it was detected, while legitimate users are unaffected.

Yes, automatically. If the user is not logged in, HashCash is injected into every CF7 form without any configuration. You can also use the [hashcash] shortcode for manual placement.

Yes. The indicator is visual feedback only — it does not interfere with screen readers or keyboard navigation. There is no interactive challenge of any kind.

Each proof-of-work calculation is timestamped. On submission, the server verifies that timestamp is within 30 minutes of the current time — this prevents replay attacks, where a bot captures a valid solution and reuses it repeatedly. HashCash automatically refreshes the calculation before it expires, so users who leave a form open for an extended period never encounter a validation failure on submission.

Yes. HashCash as a concept dates to 1997 — it was originally designed to combat email spam using proof-of-work. This plugin applies the same principle to web forms, using modern cryptographic algorithms where the original used SHA-1.