About tclient.com

tclient.com is a free set of 48 tools for the everyday work of running networks, servers and email: looking up DNS and mail records, checking certificates and security headers, converting and decoding data, generating keys and passwords, and translating commands between Windows and Linux. It began as a page of handy links and grew into the tools themselves.

How it works

No sign-up, no ads, no paywall. Every tool is usable straight away, on any device.
Your data stays yours. 33 of the tools run entirely in your browser, so the certificates, logs, configs and passwords you paste never reach our server. The privacy page lists which tools do use the server and exactly what they send where.
Answers you can check. Tools show the standard behind a result (an RFC, the CA/Browser Forum rules, Microsoft's documentation) and the command you'd run to get the same answer yourself.
Built for people who fix things. The explanations say what a finding means and what to change, not just pass or fail.

What's here

Network	My IP Details, IPv4 Subnet Calculator, Subnet Mask Cheat Sheet, IP Address Converter
DNS	DNS Lookup, CAA Lookup, TXT Lookup
Email	Email Health, MX Lookup, SPF Check, DKIM Check, Blacklist Check, Email Header Analyzer, DMARC Report Analyzer, DMARC Lookup
Certificates	TLS Certificate Checker, Certificate Decoder, Certificate Converter, Key Matcher, Chain Builder, CSR Generator, Private CA Builder, Certificate Transparency Search, CAA Record Builder
Security	Security Headers, Hash Generator, JWT Decoder, Password Breach Check
Passwords	Instant Keys, Password Generator, PSK Generator
Windows & Admin	Robocopy Command Builder, Shell Translator, PowerShell Alias Decoder
Encoding & Conversion	Base64 Encode / Decode, URL Encode / Decode, HTML Entity Encode / Decode, Number Base Converter, UUID / GUID Generator, Unix Timestamp Converter, Cron Expression Tool
Text & Data	JSON Formatter, YAML / JSON / XML Converter, CSV / JSON Converter, Case / Text Transform, Text Diff, Regex Tester (.NET), Markdown Preview

Browse all tools with descriptions.

How it's built

The site is a .NET 10 Blazor application with the MudBlazor component library. Browser tools are the same C# code compiled to WebAssembly, so they run on your device at near-native speed; lookups that have to happen on a server run there, through public DNS resolvers and with checks that stop the tools being used to reach private networks. There are no third-party scripts besides Google Analytics, and a strict Content Security Policy enforces that.

Open-source software and data

tclient.com is built with these projects. Thank you to their authors.

Project	Used for	Licence
.NET and ASP.NET Core (Blazor)	The whole site	MIT
MudBlazor	The interface components	MIT
DnsClient.NET	DNS and email lookups	Apache 2.0
MaxMind GeoIP2 .NET API	IP location lookups	Apache 2.0
Cronos, CronExpressionDescriptor	Cron Expression Tool	MIT
DiffPlex	Text Diff	Apache 2.0
YamlDotNet	YAML / JSON / XML Converter	MIT
Markdig	Markdown Preview	BSD 2-Clause
EFF large wordlist	Passphrases	CC BY 3.0 US

This product includes GeoLite data created by MaxMind, available from maxmind.com. Breached-password data comes from Have I Been Pwned.

Accuracy

The tools are tested against the standards and vendor documentation they implement, but networks are messy and documentation lags behind software. Treat results as a well-informed second opinion, and check anything important (especially before running a command that deletes data) against your own systems.