Free IT Tools for Sysadmins
33 practical tools for the things administrators do every week: check DNS, trace a failing email, verify a certificate, decode a token or convert a config file. Each tool is listed under the task it solves, with a plain sentence on when to reach for it. No sign-up, and most run in your browser.
Network & DNS
Find out where an address lives, what its DNS says, who owns a domain, and whether a host answers.
IP Address Lookup
Shows the ISP, city, country and network of an IP address, or of yours.
When to use: Use it to check where a suspicious login or mail server really comes from.
DNS Records Lookup
Queries A, AAAA, MX, TXT, NS, CNAME and other records through Cloudflare DNS over HTTPS.
When to use: Use it after a DNS change to confirm the world sees the new record.
WHOIS Lookup
Registrar, creation and expiry dates, status and name servers via RDAP.
When to use: Use it to catch a domain that is about to expire or has moved registrar.
Ping & Port Scanner
Checks whether a host answers and whether chosen TCP ports are open. Only scan systems you own or have permission to test.
When to use: Use it to prove a firewall rule or a service port is actually reachable.
IPv4 Subnet Calculator
Network address, broadcast, usable range and mask for any CIDR.
When to use: Use it when planning VLANs, DHCP scopes or firewall ranges.
Email & Exchange
Trace, test and fix mail delivery without guessing.
Email Header Analyzer
Paste raw headers to see each hop, delays and the SPF, DKIM and DMARC results.
When to use: Use it when a message is late, lands in spam or looks spoofed.
Exchange Autodiscover Check
Tests the Autodiscover DNS records and endpoints for a domain.
When to use: Use it when Outlook keeps asking for a password or cannot find the mailbox.
SPF, DKIM & DMARC Checker
Reads and validates the records, and helps you generate correct ones.
When to use: Use it before enforcing DMARC so you do not block your own mail.
Security & Trust
Check certificates, headers, links and credentials before they cause an incident.
SSL Certificate Checker
Issuer, validity dates and days remaining for a domain's certificate.
When to use: Use it to catch expiring certificates before users see a warning.
HTTP Headers Checker
Shows response headers, redirect chains and which security headers are present.
When to use: Use it to verify HSTS, X-Frame-Options and friends after a web server change.
URL Scanner / Phishing Detector
Checks a link against VirusTotal for malware and phishing.
When to use: Use it before you open a link from an unexpected email.
Hash Generator & Lookup
MD5, SHA-1, SHA-256 and SHA-512 hashes, plus a known-file lookup.
When to use: Use it to verify a download or check whether a file hash is known.
Password Strength & Generator
Scores a password and checks it against known breaches without sending the password itself.
When to use: Use it to build a password policy example or test a candidate.
JWT Decoder
Decodes a token's header and payload and shows the expiry, in your browser.
When to use: Use it when debugging OAuth and Entra sign in tokens. Never paste production secrets into any online tool you do not trust.
Random Password Generator
Cryptographically secure passwords generated locally.
When to use: Use it for service accounts and break-glass credentials.
UUID Generator
Random v4 UUIDs in bulk.
When to use: Use it for GUIDs in scripts, manifests and test data.
Data & Developer
Convert, format and test the text formats admins meet every day.
JSON Formatter & Validator
Pretty-print, minify and validate JSON.
When to use: Use it to read API and Graph responses.
YAML to JSON Converter
Converts between YAML and JSON.
When to use: Use it for Kubernetes, Ansible and pipeline files.
XML to JSON Converter
Converts between XML and JSON, keeping attributes.
When to use: Use it for legacy configs and SOAP style responses.
CSV to JSON Converter
Converts CSV and JSON, handling quotes and delimiters.
When to use: Use it to move exported reports into scripts.
Regex Tester
Tests patterns with live match highlighting.
When to use: Use it to build log filters and validation rules.
Base64 Encoder & Decoder
Encodes and decodes with correct UTF-8 handling.
When to use: Use it for certificates, tokens and encoded PowerShell payloads.
URL Encoder & Decoder
Percent-encodes and decodes URLs and components.
When to use: Use it when a query string breaks a redirect.
Unix Timestamp Converter
Converts epoch times and readable dates.
When to use: Use it to read log timestamps and token expiry values.
Text Diff Checker
Compares two texts line by line.
When to use: Use it to spot what changed between two config files.
Number Base Converter
Binary, octal, decimal, hex and any base to 36.
When to use: Use it for permissions, masks and flags.
Hash Generator (SHA-2)
SHA-1 and SHA-2 hashes of text in your browser.
When to use: Use it for quick checksums without uploading anything.
Markdown Previewer
Live side by side Markdown preview.
When to use: Use it to draft README files and runbooks.
HTML Entity Encoder
Encodes and decodes HTML entities.
When to use: Use it when special characters break a page or template.
Meta Tag Generator
SEO, Open Graph and Twitter Card tags.
When to use: Use it to prepare tags for a new page.
Windows & Deployment
Tools for the messy parts of Windows administration.
Crash Dump Analyzer
Extracts readable details from a Windows minidump or Linux core file.
When to use: Use it for a first look at a blue screen before opening a debugger.
EXE to MSI Wrapper
Wraps an .exe in a minimal MSI package.
When to use: Use it when a deployment tool only accepts MSI files.
User-Agent Parser
Breaks a User-Agent string into browser, engine, OS and device.
When to use: Use it to understand strange entries in web server logs.
How to use these tools
- Pick the category that matches your problem, such as Email & Exchange for a delivery issue.
- Open the tool and enter the domain, address, header or text.
- Read the result, then use the "when to use" note to choose the next tool.
FAQ
Are these IT tools free?
Yes. All of them are free with no sign-up. Most run entirely in your browser.
Do the tools send my data anywhere?
Client-side tools such as the JSON formatter, JWT decoder and converters process text in your browser. Network tools such as DNS, WHOIS, SSL and port checks must contact outside services to answer, and the privacy policy explains what is sent.
Can I scan any server with the port scanner?
Only scan systems you own or have written permission to test. The scanner is rate limited and refuses private and internal addresses.
Which tool should I use first when email fails?
Start with the Email Header Analyzer on a failing message, then check SPF, DKIM and DMARC, and finally Autodiscover if the problem is Outlook connecting.