diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index 0d6ff2557..353fb95bb 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -11,6 +11,10 @@ We welcome any type of contribution, not only code. You can help with
 - **Community**: presenting the project at meetups, organizing a dedicated meetup for the local community, ...
 - **Code**: take a look at the [open issues](https://github.com/HTMLHint/HTMLHint/issues). Even if you can't write code, commenting on them, showing that you care about a given issue matters. It helps us triage them.
 
+## Development setup
+
+Use Node.js 20 or later (the repo pins a version with [Volta](https://volta.sh/) in `package.json`).
+
 ## Submitting code
 
 Any code change should be submitted as a pull request. The description should explain what the code does and give steps to execute it. The pull request should also contain tests.
diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
index a2c8fbd26..726fdf5ef 100644
--- a/.github/copilot-instructions.md
+++ b/.github/copilot-instructions.md
@@ -6,7 +6,7 @@
 - All code should be formatted with Prettier.
 - Use ESLint to check for JavaScript errors.
 - Rollup is used for building the project.
-- Node v20 is used for development.
+- Node.js 20 or newer is required; Volta pins the repo to Node 20 LTS in `package.json`.
 - Core code is in TypeScript v5.4.5.
 - All new rules for HTMLHint should be placed in the rules directory.
 - Tests for new rules should be added in rules and follow the naming pattern `<rule-name>.spec.js`.
diff --git a/.github/workflows/ossf-scorecard.yml b/.github/workflows/ossf-scorecard.yml
index 364c76274..2ab0441da 100644
--- a/.github/workflows/ossf-scorecard.yml
+++ b/.github/workflows/ossf-scorecard.yml
@@ -7,6 +7,10 @@ on:
   push:
     branches: ['main']
 
+concurrency:
+  group: scorecard-${{ github.ref }}
+  cancel-in-progress: true
+
 permissions: read-all
 
 jobs:
diff --git a/.github/workflows/spellcheck.yml b/.github/workflows/spellcheck.yml
index 26be0cfab..554674c3a 100644
--- a/.github/workflows/spellcheck.yml
+++ b/.github/workflows/spellcheck.yml
@@ -6,6 +6,10 @@ on:
   pull_request:
     branches: [main]
 
+concurrency:
+  group: spellcheck-${{ github.ref }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 
diff --git a/.github/workflows/super-linter.yml b/.github/workflows/super-linter.yml
index 3ba6dc9f8..c6e0cb1dd 100644
--- a/.github/workflows/super-linter.yml
+++ b/.github/workflows/super-linter.yml
@@ -9,6 +9,10 @@ on:
     branches-ignore:
       - 'dependabot/**'
 
+concurrency:
+  group: super-linter-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f3a447e0b..d92dc3f66 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -43,7 +43,6 @@ jobs:
       fail-fast: false
       matrix:
         node:
-          - 18
           - 20
           - 22
           - 24
diff --git a/.nvmrc b/.nvmrc
index 9a2a0e219..018b52d01 100644
--- a/.nvmrc
+++ b/.nvmrc
@@ -1 +1 @@
-v20
+v20.20.1
diff --git a/README.md b/README.md
index 2db67eeb7..fc1acf41c 100644
--- a/README.md
+++ b/README.md
@@ -38,6 +38,8 @@
 
 ## 📟 Installation and Usage
 
+HTMLHint requires [Node.js](https://nodejs.org/) 20 or later.
+
 There are two ways to install HTMLHint: globally and locally.
 
 ### Local Installation and Usage
diff --git a/package-lock.json b/package-lock.json
index 204add7b2..345a84f24 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -42,7 +42,7 @@
         "typescript": "5.4.5"
       },
       "engines": {
-        "node": ">=18"
+        "node": ">=20"
       },
       "funding": {
         "type": "Open Collective",
diff --git a/package.json b/package.json
index c7b8d9773..27cfb8758 100644
--- a/package.json
+++ b/package.json
@@ -79,9 +79,9 @@
     "typescript": "5.4.5"
   },
   "engines": {
-    "node": ">=18"
+    "node": ">=20"
   },
   "volta": {
-    "node": "18.20.8"
+    "node": "20.20.1"
   }
 }
diff --git a/website/src/content/docs/getting-started.mdx b/website/src/content/docs/getting-started.mdx
index 4c9046238..817c9459e 100644
--- a/website/src/content/docs/getting-started.mdx
+++ b/website/src/content/docs/getting-started.mdx
@@ -5,6 +5,8 @@ description: How to set up HTMLHint in your project by adding it as a dev depend
 
 import { Tabs, TabItem } from '@astrojs/starlight/components';
 
+HTMLHint requires Node.js 20 or later.
+
 1\. Use npm or yarn to install HTMLHint:
 
 <Tabs>