UD5 Toolkit
DKIM Record Generator - Online Public Key DNS Entry
Generate a DKIM DNS record from a public key and selector. Check syntax. Improve your domain’s email deliverability.
Email Header Parser - Online Analyze Email Delivery Path
Email Header Analyzer
Paste the full email header below to trace the delivery path and check authentication status.
Frequently Asked Questions
An email header is the hidden part of an email containing technical details like sender and recipient addresses, subject, date, and the path the email took across mail servers. It helps diagnose delivery issues and detect spam or phishing.
Gmail: Open the email, click the three dots (More) > Show original.
Outlook: Double-click the email > File > Properties, then look under Internet headers.
Yahoo: Open the email, click More > View Raw Message.
Apple Mail: Open the email, go to View > Message > Raw Source.
Outlook: Double-click the email > File > Properties, then look under Internet headers.
Yahoo: Open the email, click More > View Raw Message.
Apple Mail: Open the email, go to View > Message > Raw Source.
Each "Received" line is added by a mail server as the email passes through it. The topmost Received header is added by the final server (recipient's), and the bottommost is from the original sender. By reading them in reverse order you can trace the exact delivery path.
SPF (Sender Policy Framework) checks that the sending server's IP is authorized to send emails for the domain. A "pass" result means the IP is allowed; "fail" often leads to spam filtering.
DKIM (DomainKeys Identified Mail) adds a digital signature to the email, verifying that the message hasn't been modified and truly comes from the claimed domain. It helps prevent email spoofing.
DMARC (Domain-based Message Authentication, Reporting, and Conformance) builds on SPF and DKIM. It tells receiving servers what to do if authentication fails (reject/quarantine/none) and provides reporting on who is sending emails from your domain.
Common reasons include missing or failed SPF/DKIM/DMARC, blacklisted IP, unusual sending patterns, or content that triggers spam filters. Use this analyzer to check if authentication passed and trace the server path.
Cookie String Parser & Editor – Read document.cookie
Parse a raw cookie string into a readable table. Edit values or create new cookies, then get the properly formatted string to set via JavaScript.
SPF Record Validator – Syntax Check & Limit Analyzer
Validate the syntax of an SPF record, check for the 10‑lookup limit, and flatten nested includes. Improve email deliverability by fixing SPF errors.
Robots.txt Validator & Parser - Online Check Syntax
Paste robots.txt content and parse it to check validity, find disallowed paths. Educational SEO tool. Local processing.
Email Header Analyzer - Online SPF, DKIM, DMARC Check
Paste raw email headers and see authentication results (SPF, DKIM, DMARC) in a readable table. Find spoofing attempts.
Advanced Set‑Cookie String Parser - Online Decode Flags
Paste a `Set‑Cookie` header and see all attributes parsed: domain, path, Max‑Age, SameSite, Secure, HttpOnly. Debug cookies easily.
Permissions‑Policy Header Parser - Online Decode & Check
Paste the Permissions‑Policy header and get a human‑readable table of allowed/blocked browser features. Understand how your site is restricted.
iCalendar File Viewer - Online ICS Parser
Drop or paste an .ics file and see all events in a readable table. Check dates, times, and locations. Privacy‑friendly.
Snowflake ID Parser - Online Decode Discord/Twitter IDs
Parse a Snowflake ID (used by Discord, Twitter) into its timestamp, worker, and sequence components. Instant local decoding.
SPF Record Generator - Online Email Authentication DNS
Build a valid SPF TXT record by selecting mail servers, IPv4/IPv6 ranges, and includes. Validate syntax and get ready‑to‑publish output.
Text to ISO Date Converter - Online Parse Any Date String
Paste a human‑readable date (like 'next Friday' or 'March 5, 2023') and convert it to ISO 8601 format. Quick and tolerant.
Web Server Log Parser - Online Apache/Nginx Analyzer
Paste a raw server log snippet and see a structured table with IP, method, URL, and status. Quick audit.
Cookie String Parser - Online Decode & Format Browser Cookies
Paste a raw cookie string and see a formatted key‑value table. Debug session cookies and understand flags. Runs in browser.
Query String Parser & Builder - Online URL Params Editor
Parse a URL's query string into a key-value table, or build a query string from parameters. Perfect for API testing and web development.
User Agent Parser - Online Browser & OS Detector
Paste a user agent string to get a human-readable breakdown of browser, operating system, and device. See your own current agent info automatically.
Crontab Guru - Online Cron Expression Parser & Translator
Describe cron schedule expressions in plain English and test future execution times. Indispensable for DevOps and backend developers. Local analysis.