Quick Difference

http://www.quickdiff.com/

An Online Tool to do a ‘quick and dirty’ diff of two text or code fragments

 

Jack of All Trades

http://sortmylist.com/ 

This is an incredible tool that can quickly reformat any text by adding, replacing, deleting, or sorting based on specified criteria.

 

htaccess Functionality Tester

https://htaccess.madewithlove.be/

To test your htaccess rewrite rules, simply fill in the url that you’re applying the rules to, place the contents of your htaccess on the larger input area and press “Test” button.

 

htaccess Syntax Tester

http://www.htaccesscheck.com/

Sick of one silly typo in a .htaccess file causing your entire site to be broken? This simple checker will validate that your .htaccess lines are free of any syntax errors.

 

PHP Code Syntax Tester

https://phpcodechecker.com/

 This free service performs a line-by-line analysis for common mistakes and errors in your PHP syntax and will not execute or save your code.

PHP Functionality Tester

http://phptester.net/

 Same as above?

REGEX Tester

https://regex101.com/

Online regex tester and debugger: PHP, PCRE, Python, Golang & JavaScript 

SSL Certificate Tester

https://www.sslshopper.com/ssl-checker.html

This SSL Checker will help you diagnose problems with your SSL certificate installation. You can verify the SSL certificate on your web server to make sure it is correctly installed, valid, trusted and doesn’t give any errors to any of your users. To use the SSL Checker, simply enter your server’s hostname (must be public) in the box below and click the Check SSL button. If you need an SSL certificate, check out the SSL Wizard. 

Redirect Checker

http://www.redirect-checker.org/index.php

 

Check your URL redirect for accuracy. Do you use search engine friendly redirections like to many redirects or do you loose link juice for seo by redirects using HTTP Statuscode 301 vs. 302. Check now!

Redirect/HTTP Status Code Tester

https://httpstatus.io/

Check status code, response headers, redirect location and redirect chain of a HTTP connection.

 

IP Address Checker

https://whatismyip.com

Lets you find an hide your IP address.

Full DNS Record Test

https://intodns.com/

IntoDNS checks the health and configuration and provides DNS report and mail servers report.

And provides suggestions to fix and improve them, with references to protocols’ official documentation.

 

DNS Propagation Check

https://www.whatsmydns.net/

whatsmydns.net lets you instantly perform a DNS lookup to check a domain names current IP address and DNS record information against multiple name servers located in different parts of the world.

This allows you to check the current state of DNS propagation after having made changes to your domains records.

MX Records

https://mxtoolbox.com/diagnostic.aspx

This test will connect to a mail server via SMTP, perform a simple Open Relay Test and verify the server has a reverse DNS (PTR) record.  It will also measure the response times for the mail server.  If you don’t know your mail server’s address, start with a MX Lookup.