toolhq.io

68+ toolsLocal-first · No account required

Paste it. Fix it.Keep it private.

Debug code, APIs, DNS, SSL, email and network issues without handing sensitive information to random online tools. Local utilities run directly on your device, and network checks say exactly what they send.

Detection runs in your browser as you type, using plain pattern matching with no network request.

Browse toolsUse toolhq with AI
  • Local-first
  • No signup required
  • Core tools free
  • Transparent network checks
Most used

The checks that start most debugging sessions. Every one opens ready to use, with no account and no setup.

JSON Formatter & ValidatorFormat, validate, and minify JSON with clear error messages and line numbers.BrowserDNS LookupQuery A, AAAA, MX, TXT, NS, SOA, CNAME, and CAA records for any domain.NetworkMCPSSL CheckerInspect a host's TLS certificate chain, expiry, trust, protocol, and hostname match.NetworkMCPJWT DecoderDecode JWT headers and payloads, inspect claims, and check expiry. Decode only, in your browser.BrowserEmail Health (SPF, DKIM, DMARC)Check a domain's SPF, DKIM, and DMARC records plus its MX, with plain-English notes.NetworkRegex TesterTest regular expressions against sample text with live match highlighting and capture groups.BrowserHTTP Header CheckerFetch a URL from the server, follow redirects, and inspect response and security headers.NetworkMCPAPI TesterSend REST requests from your browser, import or copy as cURL, and inspect the status, headers, timing, and response body.Network
Browse all 68 tools
Start here

What are you debugging?

Four areas cover most of what breaks. Pick the one closest to your problem and the right tool is one click away.

Code & Data

Read, reshape and check the payloads and values you already have in front of you.

Explore code tools

Web & APIs

Find out what a server is actually returning: status, headers, redirects, payloads.

Explore web tools

Domains & Email

Work out why a domain resolves the way it does and why mail from it is being rejected.

Explore domain tools

TLS & Certificates

Check what a host is serving, decode what you were sent, and confirm the chain holds.

Explore certificate tools
Domain health

Check everything important about a domain in one place.

Enter a domain once and run any check against it without retyping. Each check opens the tool that performs it, with the domain already loaded and the result on screen.

DNS recordsTLS certificateSPF, DKIM, DMARCMail serversHeaders and redirectsRegistration and nameserversBlacklistsDNS propagation

These checks query public DNS, public blacklists, registry data and the host itself from our server. The domain you enter is sent to make those queries and is not stored.

toolhq MCP

Give your AI agent real network diagnostics.

Connect toolhq to a compatible AI coding tool and your agent can inspect DNS, TLS, mail and HTTP infrastructure itself, instead of guessing or asking you to paste the output. The local tools keep running in your browser.

dns_lookupssl_checkmx_lookupip_lookupip_reputationhttp_headersdns_propagationreverse_dns

$ claude mcp add --transport http toolhq https://toolhq.io/api/mcp

> Check whether example.com has a valid SSL certificate.
> Verify the DNS records for example.com.
> Find the MX records for this domain.
> Inspect the HTTP response headers on this site.
One endpoint. No keys, no account.Set up toolhq MCP

Built with privacy
in mind.

Local when possible

Formatting, encoding, decoding, hashing, key handling and the generators run as plain JavaScript on your device. Once the page has loaded they keep working with no connection at all.

Transparent network checks

DNS, TLS, mail and HTTP checks cannot work without the network. Those tools carry a badge saying what is sent and where it goes, on the page, before you type anything.

No account required

The core tools need no sign up, no email address and no API key. Browser storage holds your theme, language and recently opened tools, and that list is opt in.

No unnecessary tracking

Page counts are cookieless and aggregate. There are no ad pixels and no cross-site tracking. A live chat widget from Tawk.to loads on every page and sets its own cookies; it is the one third party here and the privacy page says so.

Read the privacy page
Workflows

One problem, the checks in order.

Most issues are not one lookup, they are a sequence. Each tool ends by pointing at the next check in the task you are on, so you are never left guessing.

Mail is going to spam

Start at the mail servers, read the authentication records, then confirm the sending address is not listed anywhere.

  1. MX Lookup
  2. Email Health (SPF, DKIM, DMARC)
  3. SPF Record Generator
  4. DMARC Record Generator
  5. Blacklist Check

The certificate is not trusted

Check what the host is actually serving, decode the chain, then confirm the certificate was issued and has not been revoked.

  1. SSL Checker
  2. SSL & CSR Decoder
  3. CA Matcher
  4. CT Log Lookup
  5. OCSP Checker

The DNS change has not taken effect

Read the records you have, compare them across public resolvers, then check the registration and what the site is serving now.

  1. DNS Lookup
  2. DNS Propagation Checker
  3. Domain Registration Lookup
  4. HTTP Header Checker
Guides

Guides for the things you debug.

Practical, no-fluff writing on DNS, email authentication, TLS, HTTP and the data formats you work with, written alongside the tools that fix them.

Aug 18, 20267 min read

ARC: why forwarded mail fails SPF and DKIM

Forwarding rewrites the path and mailing lists rewrite the message, so authentication that passed at the origin fails at the destination.

Aug 18, 20268 min read

The bulk sender rules for Gmail and Yahoo, and how to meet them

Sending over 5,000 messages a day to Gmail means authentication, one-click unsubscribe and a spam rate under 0.3 percent.

Aug 18, 20267 min read

Why you cannot put a CNAME at your apex domain

Why a CNAME at your apex domain is illegal, what breaks when you force it, and how ALIAS, ANAME and CNAME flattening solve it.

Read all posts
JSON FormatterNo account requiredRegex TesterLocal-firstAPI TesterCore tools freeJWT DecoderSSL CheckerWebhook InspectorBase64Email HealthAvailable over MCPHTTP HeadersDNS Lookup
The full directory

All 68 tools.

Search or filter the complete list. Most tools run entirely in your browser; the ones that use the network say exactly what they send.

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Questions

Asked often, answered plainly.

What is toolhq?

A debugging toolbox for developers, DevOps engineers and technical teams. It covers code and data, APIs and HTTP, DNS and domains, TLS certificates, email authentication and networking. The same network checks are also available to AI coding agents over the Model Context Protocol.

Is my data sent anywhere?

It depends on the tool, and each tool says which it is. Formatters, decoders, encoders, hashing, key handling and the generators run entirely in your browser, so what you paste stays on your device. Checks that look up DNS, TLS, mail or HTTP have to reach the network, and those pages state what is sent before you type anything.

Is toolhq free?

The core browser tools are free to use, with no usage limits and no account to create. Nothing on the site is behind a sign up today.

Do I need an account?

No. There are no accounts, no sign ups and no API keys for the core tools, including the MCP endpoint.

Do the tools work offline?

The local ones do. Once a tool page has loaded, formatters, converters, encoders and generators keep working with no connection, because there is no server involved. The network checks need a connection by definition.

Can my AI agent use toolhq?

Yes. The network checks are exposed over MCP at https://toolhq.io/api/mcp, so Claude Code, Codex, Cursor and other MCP clients can run a DNS, TLS, MX, IP, propagation, reverse DNS or HTTP header check directly. No key and no account are needed.

How many tools are there?

There are 68, grouped by the problem they solve rather than listed as one long index. New ones are added when they earn a place.