H
by RicheyWeb
0 (0 reviews)
HashCash – Proof of Work CAPTCHA
Invisible Proof-of-Work CAPTCHA. No checkboxes, no image grids, no Google, no tracking. Just spam protection that gets out of the way.
Compatible with WP 7.0.2
v1.0.10
Current Version v1.0.10
Updated 1 month ago
Last Update on 15 Jun, 2026
Refreshed 7 hours ago
Last Refreshed on
Rank
#60,531
—
No change
Active Installs
0+
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No change
KW Avg Position
102.5
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No change
Downloads
80
+2 today
Support Resolved
0%
—
No change
Rating
0%
Review 0 out of 5
0
(0 reviews)
Next Milestone 10
0+
10+
31,553
Ranks to Climb
-
Growth Needed
8,000,000
Active Installs
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Rank Changes
Current
#60,531
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Overall
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5
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2
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1
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Tracked Keywords
Showing 2 of 2| Keyword | Position | Change | Type | Updated |
|---|---|---|---|---|
| antispam | 90 | — | Tag | 1 day ago |
| Proof of Work | 115 | — | Tag | 1 day ago |
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- Version
- 1.0.10
- Last Updated
- Jun 15, 2026
- Requires WP
- 6.0+
- Tested Up To
- 7.0.2
- PHP Version
- 7.4 or higher
- Author
- RicheyWeb
Support & Rating
- Rating
- ☆ ☆ ☆ ☆ ☆ 0
- Reviews
- 0
- Support Threads
- 0
- Resolved
- 0%
Keywords
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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.