# Phishing Detection APIs: What They Do and How to Use Them

> Phishing detection APIs score URLs, domains and emails for phishing risk in real time. What they check, where they fit in email and app security, and how to evaluate them.

Source: https://playciso.com/blog/phishing-detection-apis · Published: 2026-09-26 · Publisher: PlayCISO (https://playciso.com)

---

Phishing is still the most common way attackers get in, and a phishing detection API is a cheap way to add a real-time risk check to the places users encounter links. It is not a silver bullet — phishing is adversarial and fast-moving — but as one weighted layer it meaningfully raises the bar. ## What they check A phishing detection API combines several signals: blocklist and threat-feed lookups for known phishing URLs/domains; heuristics like newly-registered domains, lookalike/homoglyph names and suspicious URL structure; page and content analysis (is this imitating a login form or a known brand?); and sometimes brand-impersonation detection. ## Where they fit - Checking links in user-generated content before they are shown or clicked. - A real-time check inside email or messaging security. - Protecting sign-up, comment and message flows. - Enriching alerts and investigations with a risk signal. ## Don't rely on it alone Brand-new phishing pages may not be catalogued yet, and attackers evade detection actively. Use the API as one weighted layer alongside user training, email authentication (SPF/DKIM/DMARC), phishing-resistant MFA and easy reporting. Block obvious hits, challenge uncertain ones. ## How to evaluate Test against known-phishing and known-legitimate URLs from your own environment; measure detection rate _and_ false positives. Check freshness, coverage, latency, rate limits/pricing (free tiers exist), and how they handle the URLs you submit. Check indicators with the free [Reputation Checker →](/tools/reputation-checker) and browse the [Security APIs directory](/security-apis). ## Frequently asked questions **What does it check?** Blocklists, domain/URL heuristics (new/lookalike domains), page/content analysis, brand impersonation. **Where does it fit?** Link checks in UGC, email/messaging security, sign-up/comment flows, alert enrichment. **Rely on it alone?** No — combine with training, SPF/DKIM/DMARC, phishing-resistant MFA and reporting. **How to evaluate?** Test on your own URLs for detection and false positives; check freshness, latency, limits, privacy.