{"id":592,"date":"2025-09-26T22:21:00","date_gmt":"2025-09-26T20:21:00","guid":{"rendered":"https:\/\/extendsclass.com\/blog\/?p=592"},"modified":"2024-03-12T09:04:24","modified_gmt":"2024-03-12T07:04:24","slug":"best-free-online-developer-tools","status":"publish","type":"post","link":"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools","title":{"rendered":"Essential Free Online Resources for Developers"},"content":{"rendered":"\n<p>We are fortunate to have a plethora of free online development tools at our disposal, which can make our lives as developers easier. In this article, I will present the ones that I find interesting and that I wanted to share with you.<\/p>\n\n\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_47_1 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"ez-toc-toggle-icon-1\"><label for=\"item-69da037f50064\" aria-label=\"Table of Content\"><span style=\"display: flex;align-items: center;width: 35px;height: 30px;justify-content: center;direction:ltr;\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/label><input  type=\"checkbox\" id=\"item-69da037f50064\"><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#Tools_for_regular_expressions\" title=\"Tools for regular expressions\">Tools for regular expressions<\/a><ul class='ez-toc-list-level-3'><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#Regex101_%E2%80%93_Creating_testing_and_debugging_regular_expressions\" title=\"Regex101 &#8211; Creating, testing, and debugging regular expressions\">Regex101 &#8211; Creating, testing, and debugging regular expressions<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#Cyrilex_%E2%80%93_Regular_Expression_Tester_and_Visualizer\" title=\"Cyrilex &#8211; Regular Expression Tester and Visualizer\">Cyrilex &#8211; Regular Expression Tester and Visualizer<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#Data_set_generators\" title=\"Data set generators\">Data set generators<\/a><ul class='ez-toc-list-level-3'><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#Mockaroo_%E2%80%93_Generating_realistic_test_data\" title=\"Mockaroo &#8211; Generating realistic test data\">Mockaroo &#8211; Generating realistic test data<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#Mockium_%E2%80%93_Freely_generate_large_datasets\" title=\"Mockium &#8211; Freely generate large datasets\">Mockium &#8211; Freely generate large datasets<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#Playgrounds\" title=\"Playgrounds\">Playgrounds<\/a><ul class='ez-toc-list-level-3'><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#Codepenio_%E2%80%93_Test_and_showcase_excerpts_of_HTML_CSS_and_JavaScript_code\" title=\"Codepen.io &#8211; Test and showcase excerpts of HTML, CSS, and JavaScript code\">Codepen.io &#8211; Test and showcase excerpts of HTML, CSS, and JavaScript code<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#DB_Fiddle_%E2%80%93_MySQL_and_PostgreSQL_sandbox\" title=\"DB Fiddle &#8211; MySQL and PostgreSQL sandbox\">DB Fiddle &#8211; MySQL and PostgreSQL sandbox<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#A_medley_of_cool_tools\" title=\"A medley of cool tools\">A medley of cool tools<\/a><ul class='ez-toc-list-level-3'><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#Codebeautifyorg_%E2%80%93_The_Ali_Baba%E2%80%99s_cave\" title=\"Codebeautify.org &#8211; The Ali Baba&#8217;s cave\">Codebeautify.org &#8211; The Ali Baba&#8217;s cave<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#Freeformattercom_%E2%80%93_Online_developer_tools\" title=\"Freeformatter.com &#8211; Online developer tools\">Freeformatter.com &#8211; Online developer tools<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/extendsclass.com\/blog\/best-free-online-developer-tools\/#Pythoniumnet_%E2%80%93_For_Python_developers\" title=\"Pythonium.net &#8211; For Python developers\">Pythonium.net &#8211; For Python developers<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Tools_for_regular_expressions\"><\/span>Tools for regular expressions<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>To begin with, regular expressions are a powerful tool for developers. However, unfortunately, they can also be the bane of many developers&#8217; existence. Crafting or correcting a regular expression can quickly become a hair-pulling experience.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Regex101_%E2%80%93_Creating_testing_and_debugging_regular_expressions\"><\/span>Regex101 &#8211; Creating, testing, and debugging regular expressions<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"458\" src=\"https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/regex101-1024x458.png\" alt=\"\" class=\"wp-image-602\"\/><\/figure>\n\n\n\n<p><a href=\"https:\/\/regex101.com\/\" title=\"\">Regex101 <\/a>is a comprehensive online tool designed to assist developers in working with regular expressions. It provides a user-friendly interface for creating, testing, and debugging regular expressions in various programming languages, including JavaScript, Python, PHP, and many others. With features like syntax highlighting, real-time matching, explanation of regex patterns, and substitution support, Regex101 simplifies the process of working with regular expressions, making it a valuable resource for both beginners and experienced developers alike.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Cyrilex_%E2%80%93_Regular_Expression_Tester_and_Visualizer\"><\/span>Cyrilex &#8211; Regular Expression Tester and Visualizer<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"462\" src=\"https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/cyrilex-1024x462.png\" alt=\"\" class=\"wp-image-604\"\/><\/figure>\n\n\n\n<p>I will try to remain neutral, <a href=\"https:\/\/extendsclass.com\/regex-tester.html\" title=\"\">Cyrilex <\/a>is a regular expression tester offering numerous features. Like regex101, it allows testing regex in different programming languages, including MySQL (a rare feature among competitors). It includes a pattern visualizer, which makes it easier to understand patterns. It also offers the ability to generate strings from a pattern.<\/p>\n\n\n\n<p><\/p>\n\n\n\n<p>For beginners, if you are not familiar with regex and do not know when to use them, you can refer to the following article: <a href=\"https:\/\/datascientest.com\/en\/demystifying-regular-expressions-regex-definition-and-practical-usage\">https:\/\/datascientest.com\/en\/demystifying-regular-expressions-regex-definition-and-practical-usage<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Data_set_generators\"><\/span>Data set generators<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Data generators are invaluable for creating diverse and representative data for testing purposes, ensuring robustness and accuracy in software evaluation and performance analysis.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Mockaroo_%E2%80%93_Generating_realistic_test_data\"><\/span>Mockaroo &#8211; Generating realistic test data<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"441\" src=\"https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/mockaroo-1024x441.png\" alt=\"\" class=\"wp-image-606\"\/><\/figure>\n\n\n\n<p><a href=\"https:\/\/www.mockaroo.com\/\">Mockaroo<\/a> is a versatile online tool designed for generating realistic test data. With Mockaroo, you can easily create customized datasets for testing purposes in various formats, including CSV, JSON, SQL, and Excel. It offers a wide range of data types and options for generating structured and randomized data, allowing you to simulate real-world scenarios accurately. Additionally, Mockaroo provides features such as data validation and custom formulas. Whether you are a developer, tester, or data analyst, Mockaroo is an invaluable resource for creating realistic test data efficiently.<\/p>\n\n\n\n<p>Mockaroo also offers a paid version with numerous advantages and removes certain limitations. It is also available as a docker image that you can deploy in your own private cloud.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Mockium_%E2%80%93_Freely_generate_large_datasets\"><\/span>Mockium &#8211; Freely generate large datasets<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"438\" src=\"https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/mockium-1024x438.png\" alt=\"\" class=\"wp-image-607\"\/><\/figure>\n\n\n\n<p><a href=\"https:\/\/softwium.com\/mockium\/\" title=\"\">Mockium <\/a>enables rapid generation of test data without the need for registration or installation. Like Mockaroo, you visually define your dataset fields and select data types, with predefined types corresponding to typical client data found in datasets. You can generate dummy data files (CSV, SQL, JSON) according to your specifications. However, its advantage lies in the <strong>absence of limitations<\/strong> on the quantity of generated data; you can freely <strong>generate large datasets <\/strong>with hundreds of thousands of elements at <strong>no cost<\/strong>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Playgrounds\"><\/span>Playgrounds<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Playgrounds serve as invaluable platforms for developers to explore and learn. They enable rapid experimentation and testing. Furthermore, they facilitate seamless sharing troubleshooting on forums (Yes, ChatGPT hasn&#8217;t killed forums yet).<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Codepenio_%E2%80%93_Test_and_showcase_excerpts_of_HTML_CSS_and_JavaScript_code\"><\/span>Codepen.io &#8211; Test and showcase excerpts of HTML, CSS, and JavaScript code<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"423\" src=\"https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/codepen-1024x423.png\" alt=\"\" class=\"wp-image-616\" srcset=\"https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/codepen-1024x423.png 1024w, https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/codepen-300x124.png 300w, https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/codepen-768x317.png 768w, https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/codepen-1536x635.png 1536w, https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/codepen-816x337.png 816w, https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/codepen.png 1917w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p><a href=\"https:\/\/codepen.io\/pen\/\" title=\"\">Codepen.io<\/a> serves as a collaborative platform tailored for front-end designers and developers. It enables to create and launch websites, showcase projects, create test scenarios for learning and debugging, and seek creative inspiration.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"DB_Fiddle_%E2%80%93_MySQL_and_PostgreSQL_sandbox\"><\/span>DB Fiddle &#8211; MySQL and PostgreSQL sandbox<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"466\" src=\"https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/db-fiddle-1024x466.png\" alt=\"\" class=\"wp-image-609\"\/><\/figure>\n\n\n\n<p><a href=\"https:\/\/www.db-fiddle.com\/\" title=\"\">db-fiddle.com<\/a> allows to create and share SQL queries across popular database engines like MySQL, PostgreSQL, and SQLite. It offers a user-friendly interface and features for sharing code snippets.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"A_medley_of_cool_tools\"><\/span>A medley of cool tools<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Codebeautifyorg_%E2%80%93_The_Ali_Baba%E2%80%99s_cave\"><\/span>Codebeautify.org &#8211; The Ali Baba&#8217;s cave<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"470\" src=\"https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/codebeautify-1024x470.jpg\" alt=\"\" class=\"wp-image-611\"\/><\/figure>\n\n\n\n<p><a href=\"https:\/\/codebeautify.org\/\" rel=\"nofollow\" title=\"\">Codebeautify.org<\/a>  offers over 100 online tools, including Code Formatters, Data Beautifiers, Viewers, Converters, and more.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Freeformattercom_%E2%80%93_Online_developer_tools\"><\/span>Freeformatter.com &#8211; Online developer tools<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"450\" src=\"https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/freeformatter-1024x450.png\" alt=\"\" class=\"wp-image-613\"\/><\/figure>\n\n\n\n<p><a href=\"https:\/\/www.freeformatter.com\" rel=\"nofollow\" title=\"\">Freeformatter.com<\/a> also offers a multitude of online tools, including formatters, validators, converters, escapers, as well as web resources (such as a list of MIME types, URL parser, etc.).<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Pythoniumnet_%E2%80%93_For_Python_developers\"><\/span>Pythonium.net &#8211; For Python developers<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"436\" src=\"https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/pythonium-1024x436.png\" alt=\"\" class=\"wp-image-756\" srcset=\"https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/pythonium-1024x436.png 1024w, https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/pythonium-300x128.png 300w, https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/pythonium-768x327.png 768w, https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/pythonium-1536x654.png 1536w, https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/pythonium-816x347.png 816w, https:\/\/extendsclass.com\/blog\/wp-content\/uploads\/2024\/06\/pythonium.png 1896w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p><a href=\"https:\/\/pythonium.net\/\" rel=\"nofollow\" title=\"\">Pythonium.net <\/a>offers a some online tools for Python developers, including formatter, validator and an online visual regex tester.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>We are fortunate to have a plethora of free online development tools at our disposal, which can make our lives as developers easier. In this article, I will present the ones that I find interesting and that I wanted to share with you. Tools for regular expressions To begin with, regular expressions are a powerful [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":602,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_sitemap_exclude":false,"_sitemap_priority":"","_sitemap_frequency":""},"categories":[2],"tags":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/extendsclass.com\/blog\/wp-json\/wp\/v2\/posts\/592"}],"collection":[{"href":"https:\/\/extendsclass.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/extendsclass.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/extendsclass.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/extendsclass.com\/blog\/wp-json\/wp\/v2\/comments?post=592"}],"version-history":[{"count":16,"href":"https:\/\/extendsclass.com\/blog\/wp-json\/wp\/v2\/posts\/592\/revisions"}],"predecessor-version":[{"id":594,"href":"https:\/\/extendsclass.com\/blog\/wp-json\/wp\/v2\/posts\/592\/revisions\/594"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/extendsclass.com\/blog\/wp-json\/wp\/v2\/media\/602"}],"wp:attachment":[{"href":"https:\/\/extendsclass.com\/blog\/wp-json\/wp\/v2\/media?parent=592"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/extendsclass.com\/blog\/wp-json\/wp\/v2\/categories?post=592"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/extendsclass.com\/blog\/wp-json\/wp\/v2\/tags?post=592"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}