{"id":7210,"date":"2024-02-14T09:19:54","date_gmt":"2024-02-14T09:19:54","guid":{"rendered":"https:\/\/metaschool.so\/articles\/?p=7210"},"modified":"2024-02-14T09:19:57","modified_gmt":"2024-02-14T09:19:57","slug":"spdx-license-identifier","status":"publish","type":"post","link":"https:\/\/metaschool.so\/articles\/spdx-license-identifier\/","title":{"rendered":"How to Resolve the &#8220;Warning: SPDX license identifier not provided in source file&#8221; Warning in Solidity?"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_56_1 ez-toc-wrap-left counter-hierarchy ez-toc-counter ez-toc-custom 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\"><\/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:\/\/metaschool.so\/articles\/spdx-license-identifier\/#Purpose_of_SPDX_license_identifiers_in_Solidity_contracts\" title=\"Purpose of SPDX license identifiers in Solidity contracts\">Purpose of SPDX license identifiers in Solidity contracts<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/metaschool.so\/articles\/spdx-license-identifier\/#Consequences_of_not_including_SPDX_license_identifier\" title=\"Consequences of not including SPDX license identifier\">Consequences of not including SPDX license identifier<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/metaschool.so\/articles\/spdx-license-identifier\/#Coding_example\" title=\"Coding example\">Coding example<\/a><ul class='ez-toc-list-level-3'><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/metaschool.so\/articles\/spdx-license-identifier\/#Non-open_source_code\" title=\"Non-open source code\">Non-open source code<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/metaschool.so\/articles\/spdx-license-identifier\/#Open_source_code\" title=\"Open source code\">Open source code<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/metaschool.so\/articles\/spdx-license-identifier\/#Conclusion\" title=\"Conclusion\">Conclusion<\/a><\/li><\/ul><\/nav><\/div>\n\n<p>Before identifying the solution for\u00a0<code>Warning: SPDX license identifier not provided in source file<\/code>\u00a0warning, let\u2019s explore what is the role of SPDX license identifier in <a href=\"https:\/\/metaschool.so\/articles\/guide-solidity-contracts\/\" target=\"_blank\" rel=\"noreferrer noopener\">Solidity<\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"purpose-of-spdx-license-identifiers-in-solidity-contracts\"><span class=\"ez-toc-section\" id=\"Purpose_of_SPDX_license_identifiers_in_Solidity_contracts\"><\/span><strong>Purpose of SPDX license identifiers in Solidity contracts<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<ol class=\"wp-block-list\"><li>The purpose of SPDX (Software Package Data Exchange) license identifiers in Solidity contracts is to provide clear and standardized information about the licensing terms under which the code is distributed.<\/li><li>SPDX helps define the rights and permissions associated with using, modifying, and sharing the code. This practice enhances transparency and facilitates collaboration within the open-source community.<\/li><\/ol>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"consequences-of-not-including-spdx-license-identifier\"><span class=\"ez-toc-section\" id=\"Consequences_of_not_including_SPDX_license_identifier\"><\/span><strong>Consequences of not including SPDX license identifier<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>If you do not include an SPDX license identifier in your Solidity <a href=\"https:\/\/metaschool.so\/articles\/structure-of-a-smart-contract\/\" target=\"_blank\" rel=\"noreferrer noopener\">contract<\/a>, it may lead to ambiguity regarding the licensing terms. And you may see the following warning:\u00a0<code>Warning: SPDX license identifier not provided in source file<\/code>.<\/p>\n\n\n\n<p>\ud83d\udd25\u00a0<strong>Check this course out:<\/strong>\u00a0<a href=\"https:\/\/metaschool.so\/courses\/how-to-write-a-smart-contract-and-mint-elon-musk-nft-on-opensea\" target=\"_blank\" rel=\"noreferrer noopener\">Write an\u00a0Elon Musk NFT Smart Contract on OpenSea<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"coding-example\"><span class=\"ez-toc-section\" id=\"Coding_example\"><\/span>Coding example<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>To address the warning, you can add an SPDX license identifier comment to your contract.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ No SPDX-License-Identifier included\npragma solidity ^0.8.0;\n\ncontract ExampleContract {\n    uint256 public data;\n\n    constructor(uint256 _data) {\n        data = _data;\n    }\n}\n<\/code><\/pre>\n\n\n\n<p><strong>Explanation<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\"><li>First, we added the comment for the SPDX identifier. It is the best practice to add this at the start of the file.<\/li><li>Next, we defined the Solidity version, which is the common practice in any Solidity coding file.<\/li><li>At last, we added the example contract.<\/li><\/ol>\n\n\n\n<p>To resolve the warning, developers should add an SPDX license identifier comment to their contract. Let\u2019s highlight two scenarios.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"non-open-source-code\"><span class=\"ez-toc-section\" id=\"Non-open_source_code\"><\/span><strong>Non-open source code<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>For non-open source code, developers can use the following SPDX identifier:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ SPDX-License-Identifier: UNLICENSED\npragma solidity ^0.7.5;\n\ncontract TestContract {\n    \/\/ Some logic\n}\n<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"open-source-code\"><span class=\"ez-toc-section\" id=\"Open_source_code\"><\/span>Open source code<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>For open-source code, developers should choose an appropriate open-source license. An example with the MIT license is provided<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ SPDX-License-Identifier: MIT\npragma solidity ^0.7.5;\n\ncontract TestContract {\n    \/\/ Some logic\n}\n<\/code><\/pre>\n\n\n\n<p><strong>\ud83d\udd25 Check this course out:<\/strong>\u00a0<a href=\"https:\/\/metaschool.so\/courses\/create-your-own-ethereum-token-in-just-30-mins\" target=\"_blank\" rel=\"noreferrer noopener\">Create Your Own Ethereum Token in Just 30 Mins<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"conclusion\"><span class=\"ez-toc-section\" id=\"Conclusion\"><\/span>Conclusion<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Adding the SPDX comment helps in providing clarity about the licensing terms for your code. Although SPDX license identifiers may not affect the functionality or deployment of your\u00a0contract, adding\u00a0them is considered good practice, especially when sharing or publishing your code.<\/p>\n\n\n\n<p><strong>Try it out and let us know how it went by tagging Metaschool on Social Media.<\/strong><\/p>\n\n\n\n<p><strong>Follow us on<\/strong>&nbsp;\u2013<\/p>\n\n\n\n<p>\ud83d\udd2eTwitter \u2013\u00a0<a href=\"https:\/\/twitter.com\/0xmetaschool\" target=\"_blank\" rel=\"noreferrer noopener\">https:\/\/twitter.com\/0xmetaschool<\/a><\/p>\n\n\n\n<p>\ud83d\udd17LinkedIn \u2013\u00a0<a href=\"https:\/\/www.linkedin.com\/company\/0xmetaschool\/\" target=\"_blank\" rel=\"noreferrer noopener\">https:\/\/www.linkedin.com\/company\/0xmetaschool\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":15,"featured_media":7215,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"neve_meta_sidebar":"","neve_meta_container":"","neve_meta_enable_content_width":"","neve_meta_content_width":0,"neve_meta_title_alignment":"","neve_meta_author_avatar":"","neve_post_elements_order":"","neve_meta_disable_header":"","neve_meta_disable_footer":"","neve_meta_disable_title":"","footnotes":""},"categories":[292],"tags":[31,46,63,324,29],"class_list":["post-7210","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-answers","tag-ethereum-blockchain","tag-solidity","tag-solidity-developers","tag-spdx","tag-web3"],"_links":{"self":[{"href":"https:\/\/metaschool.so\/articles\/wp-json\/wp\/v2\/posts\/7210","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/metaschool.so\/articles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/metaschool.so\/articles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/metaschool.so\/articles\/wp-json\/wp\/v2\/users\/15"}],"replies":[{"embeddable":true,"href":"https:\/\/metaschool.so\/articles\/wp-json\/wp\/v2\/comments?post=7210"}],"version-history":[{"count":5,"href":"https:\/\/metaschool.so\/articles\/wp-json\/wp\/v2\/posts\/7210\/revisions"}],"predecessor-version":[{"id":7218,"href":"https:\/\/metaschool.so\/articles\/wp-json\/wp\/v2\/posts\/7210\/revisions\/7218"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/metaschool.so\/articles\/wp-json\/wp\/v2\/media\/7215"}],"wp:attachment":[{"href":"https:\/\/metaschool.so\/articles\/wp-json\/wp\/v2\/media?parent=7210"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/metaschool.so\/articles\/wp-json\/wp\/v2\/categories?post=7210"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/metaschool.so\/articles\/wp-json\/wp\/v2\/tags?post=7210"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}