SynthGuard vs Undetectable.ai — browser-only privacy vs cloud rewriting.
Undetectable.ai sends your text to their servers for rewriting. SynthGuard runs entirely in your browser — same humanization quality, zero data leakage.
| Feature | SynthGuard | Undetectable.ai |
|---|---|---|
| Where text is processed | Your browser only | Their servers |
| Data logging | None — nothing leaves your device | Per their privacy policy |
| Image humanization | Yes — full pipeline | No |
| Video humanization | Yes | No |
| AI image detector | Yes — free | No |
| Pricing model | Free + €19/mo Pro | Subscription, per-word limits |
| Offline use after first load | Yes | No (requires server roundtrip) |
| Burstiness meter | Live, in-browser | Score after rewrite |
Undetectable.ai is the most well-known text humanizer. Its rewrite quality is solid for English content, and its UI is polished. The fundamental tradeoff is that every word you paste into Undetectable.ai goes to their servers for processing. Their privacy policy lays out what they do with that data — read it before pasting anything sensitive.
SynthGuard takes the opposite architectural decision. The entire humanization pipeline (contractions, phrase-replace, sentence-restructure, punctuation jitter, optional unicode tricks) runs as TypeScript inside your browser tab. Open the page once — you can disconnect from the internet and keep humanizing.
On rewrite quality, both tools target the same signals: perplexity, burstiness, n-gram overlap. SynthGuard's phrase-replace dictionary covers 400+ patterns in English and German, which is competitive with Undetectable.ai's English-only coverage. Where SynthGuard wins is the live burstiness meter — you can see your score climbing as the layers apply, not just after-the-fact.
Beyond text, SynthGuard does what Undetectable.ai doesn't: image humanization (against detectors like Hive, Sightengine, Illuminarty) and video humanization. If you only need text, Undetectable.ai is a fine choice if you trust their data handling. If you want privacy or want one tool that handles text + image + video, SynthGuard is the practical pick.
Pricing: SynthGuard is free for 3 humanizations per week, €19/month for 50, €49/month unlimited. Undetectable.ai's pricing is per-word with monthly subscription tiers. For typical use, SynthGuard's flat pricing is cheaper.
Try SynthGuard — free account, no card required
Free tier: 3 credits per week. Pro: $14.99/mo for 50 credits, all camera profiles, video export and advanced controls.
Open the humanizerFrequently asked questions
Is SynthGuard's rewrite quality as good as Undetectable.ai?+
On the detectors that matter (GPTZero, Originality.ai, Turnitin), yes. Both target the same underlying signals.
Can Undetectable.ai see my text?+
Their servers receive every word you submit. Their privacy policy describes their data handling.
Does SynthGuard work offline?+
Yes — after the page loads, the entire pipeline runs without network access.
Which one is better for non-English text?+
SynthGuard ships native German support. Undetectable.ai supports English primarily.
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