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Guerrilla Mail vs Slack

Same instrument, two spec sheets — measured, not claimed.

APIGuerrilla MailNEW—SlackNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthnoneapiKey
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree tier — API key required
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Guerrilla Mail vs Slack: common questions

Which is more reliable, Guerrilla Mail or Slack?

On our scheduled checks, Slack leads on measured uptime — Guerrilla Mail at —% versus Slack at —% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Do Guerrilla Mail and Slack need an API key?

Guerrilla Mail needs no key, while Slack requires a free API key. If you want to start calling without signup, reach for Guerrilla Mail first.

Can I call Guerrilla Mail and Slack from the browser?

Yes — both Guerrilla Mail and Slack send CORS headers over HTTPS, so front-end code can fetch either directly with no backend proxy. That makes them easy to swap in a client-side app while you compare responses.

Are Guerrilla Mail and Slack free for commercial use?

Guerrilla Mail has unclear commercial terms, and Slack has unclear commercial terms. We track service terms and the data license as separate fields — see the Commercial use and Data license rows above, and confirm both before shipping either in a paid product.