Synth Antispam is a spam filter for WordPress comments aimed at site owners who find that keyword blocklists let through polite, well-written spam while sometimes catching genuine visitors.
Instead of matching text against static word lists, it looks at what a comment is actually trying to promote, which helps it catch disguised links, fake compliments carrying a casino or crypto link, and reworded spam that slips past rule-based filters.
The plugin sends each new comment to the Synth Antispam cloud service, an AI classifier, to get a verdict on whether it is spam and why. No API key from a third-party AI provider is needed: setup works through a one-click site key issued by the service itself.
Verdicts appear directly inside WordPress, in a column added to the Comments list and, for WooCommerce shops, on the Products > Reviews screen, showing the spam category and confidence behind each decision.
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Key Features of Synth Antispam
Spam Detection
Intent-based spam recognition. Synth reads what a comment is promoting rather than matching known words or domains, so it recognizes SEO links, casino, crypto, adult and pharma pitches, and fake flattery comments carrying a link, even when the wording is rewritten or misspelled.
Coverage beyond the comment form. Checks apply to pingbacks, trackbacks, and automated submissions sent through the REST API or XML-RPC, not only comments typed into the standard form.
No keyword lists to maintain. There are no blocklists, keyword rules or regular expressions to update, since the classifier works from the meaning of the message rather than fixed patterns.
Moderation Behavior
No automatic deletion. Flagged comments go to the Spam folder, or to the moderation queue when strict mode is on, and can be restored with one click; comments are never moved to Trash automatically.
Works alongside existing moderation. Synth leaves alone any comment already marked spam or trash by a moderator or another plugin such as Akismet, and never publishes a comment that was held for review, so it can run next to existing setups without conflict.
Visible, explainable verdicts. A verdict column on the Comments list, and on the WooCommerce Reviews screen, shows the spam category and confidence score behind each checked item instead of a plain yes or no.
No visitor friction. There is no CAPTCHA, puzzle or extra form field, and no tracking script added to pages; the comment form waits briefly for a verdict while the check runs in the background.
Fallback when checks are unavailable. If the classification service cannot be reached or the included check allowance is used up, comments simply continue through normal WordPress moderation, or are held for review if that option is chosen, so the comment form keeps working.
WooCommerce and Contact Form 7
WooCommerce product review screening. Product reviews submitted through the standard WordPress comment form are checked the same way as comments, with no extra setup once a site key is in place, and reviewers with an already-approved comment or review are skipped.
Contact Form 7 submission checks. Submissions to Contact Form 7 forms can be checked for spam intent as well, with spam marked so its email is never sent; installing Flamingo keeps a record of every submission for reference.
How to Install Synth Antispam
Step 1: Install and activate. From the WordPress dashboard, go to Plugins > Add New Plugin, search for Synth Antispam, click Install Now, then Activate.
Step 2: Get a site key. Open Settings > Synth Antispam and press Get a site key, or paste in a key you already have; no account or API key copying is required.
Step 3: Test the connection. Press Test connection on the settings page to confirm the plugin can reach the classification service.
Step 4: Choose moderation behavior. Optionally select the Spam folder or strict moderation queue mode, and decide what should happen to comments if the service is unreachable or the check allowance runs out.
Step 5: Enable Contact Form 7 checks if needed. Visit Settings > Synth Antispam > Contact Form 7 to turn on checking of form submissions for spam.
Good to Know About Synth Antispam
According to the plugin’s documentation, no requests are sent to the classification service until a site key is created, aside from the request made when pressing the Get a site key button.
The developer notes that only limited data travels off-site for each check: comment text, author name and URL, the email domain, and a salted per-site hash of the email, never the full address, IP, raw user agent, or post content. Commenters with an already approved comment are skipped entirely.
Verdict records expire after 24 hours, but the service separately retains copies of submissions and verdicts indefinitely to improve its models, a setting the documentation says cannot currently be disabled. Site owners handling personal data are advised to disclose this processing in their privacy policy.
Download Synth Antispam on WordPress.org