Free Tools

Tools for developers and SREs.

Calculators, references, and guides. No signup required.

CHECKERS

Response Time Checker

Test your site from multiple global probe locations. See DNS, TCP, TLS, and TTFB breakdown for each.

Check your SSL certificate details: expiry, issuer, TLS version, and cipher suite.

Check if your DNS changes have propagated across major public resolvers.

CALCULATORS

How much downtime does your SLA actually allow? Enter a percentage, see the answer per day, week, month, and year.

Build cron expressions visually. Pick your schedule, see the expression, and preview the next runs.

REFERENCES

Every status code explained in plain language. What it means, common causes, how to fix it, and what it means for monitoring.

UPTIME TIERS

99%

Two nines

3d 15h 36m/year

99.9%

Three nines

8h 45m 36s/year

99.99%

Four nines

52m 33s/year

99.999%

Five nines

5m 15s/year

Larm uses multi-probe voting to eliminate false alerts. Checks from multiple global locations, alerts only when it's real. Free to start.