Validate DNS records — A, MX, TXT, SPF, DKIM, DMARC syntax and coherence. Catch the missing SPF that tanks deliverability — local checks, free, no signup.
Content reviewed October 2026 · About Toolzum
Validate robots.txt syntax — user-agents, allow/disallow, sitemaps, wildcards. Catch the Disallow: / that deindexed everything — local validation, free, no signup.
Validate CSS syntax — unclosed braces, bad properties, bad values — with line numbers. Catch the missing } breaking layouts — local validation, free, no signup.
Validate package.json for required fields, semver format, and dependency presence. Catch missing fields and bad semver before installs fail — free, local, no signup.
Validate IBAN structure, length, and mod-97 check digits for 80+ countries. Catch transfer typos before money moves — local ibantools work, free, no signup.
Validate canonical tags — protocol, www, trailing slash, and page consistency. Catch the canonical pointing at staging — local checks, free, no signup.
Missing SPF, misaligned DKIM, or absent DMARC policy are the top trio. Validate all three records — one gap poisons the set.
Ten DNS-query mechanisms maximum — nested includes burn through fast. Flatten vendors to cut lookups under the cap.
None (monitor) → quarantine → reject, over weeks with report review. Jumping straight to reject bounces legitimate mail on misconfigurations.
No — validation runs locally in your browser against pasted records. Nothing leaves your device.
DNS Lookup Generator
Look up live A, AAAA, CNAME, MX, TXT, and NS records via DNS-over-HTTPS. Queries go to Google DNS — results display here.
Subdomain Finder
Discover subdomains via public certificate records plus live DNS checks of common names. Read-only lookups run from your browser — the domain you check is visible to crt.sh and Google DNS, as with any lookup.