HTML Viewer is a lightweight browser-side front-end code editor and real-time preview runner, which solves the pain point of difficult cross-checking between source code and rendered page effect in daily front-end writing and learning.
Its most distinctive core capability is two-way synchronized highlighting between code editor and preview window: click a piece of code on the left, the matching element on the preview page will be marked; pick any content on the preview page, and the editor will instantly jump to and highlight the corresponding source code lines. This feature greatly speeds up error troubleshooting, element positioning and code comprehension, whether you are modifying page layout or learning how markup renders web pages.
Beyond code linkage lookup, the platform also supports direct visual editing on the preview panel. You can bold text, adjust font sizes, insert images and generate lists directly on the rendered page without manually typing HTML tags one by one. The system will automatically generate standard source code synchronously, which effectively reduces repetitive mechanical coding work and improves work efficiency for both developers and learners.
The whole tool requires no software download, no account registration, and all file parsing and preview rendering are completed locally in your browser, so your code content will not be uploaded to any external server, fully protecting your code privacy. It also supports local file import, one-click code formatting, syntax error repair and file export, forming a complete closed-loop workflow from importing materials to exporting finished files.
Suitable Crowd
Front-end developers who need to quickly debug HTML snippets and check page structure
Students and self-learners who are just getting started with web front-end basics
UI designers who need to verify simple static page prototype effects
Testing personnel who need to quickly view webpage source code and locate display problems
Hobbyists who make small static web pages and simple web demos
Core Functional Details
1. Bidirectional Code-Preview Highlight & Mapping
Code to Preview: Select any HTML, CSS or JS code fragment, the corresponding DOM node on the preview side will be highlighted with a border mark
Preview to Code: Select text, pictures or any block element on the preview page, the editor automatically locates the exact source code position and highlights the code segment
Turn off the linkage synchronization with one click to enter pure editing mode when you need to write a large amount of code continuously without interference
2. WYSIWYG Visual Editing on Preview Side
Activate the visual edit button above the preview area to call up the formatting toolbar, supporting these operations directly on the rendered page:
Text style: bold, italic, underline, font size modification, paragraph alignment
Every edit action automatically generates and updates the source code in the left editor panel in real time
3. Practical File & Code Auxiliary Tools
✅ Import local HTML/CSS/JS files from your device into the editor
✅ One-click code formatting to unify indentation and typesetting for disorganized code
✅ HTML syntax error detection and intelligent one-click repair
✅ Expand or collapse all code blocks to facilitate reading long nested documents
✅ Export the edited source file back to local storage for saving and delivery
✅ Toggle dark mode to reduce eye strain during long editing sessions
✅ Open preview page or source code page in a separate new browser tab
Screenshot 2: Preview area visual editing function display
Optional Demo Video
File name: two-way-highlight-demo.mp4
The video records the complete operation process of bidirectional highlighting linkage and preview-side visual editing, intuitively showing the core experience of the tool.
Paste your prepared HTML, CSS and JavaScript code into the left editor, or click import to load local files
The right preview area will render the webpage effect synchronously in real time
Use the two-way highlighting feature to quickly check the correspondence between code and page elements
Click the visual edit button above the preview window to modify page content directly on the rendered page
After finishing writing and debugging, use the format button to organize the code, and export the file to your local computer
Privacy & Security Statement
All code analysis, page rendering and file processing are executed locally inside the user’s browser. The platform will not collect, upload or store any of your source code and file content, and will not transmit data to any third-party servers.
Open Source License
MIT License
Free for personal learning, non-commercial use, secondary modification and open source distribution.
HTML Viewer | Browser Native Two-Way Synced HTML/CSS/JS Editor
🔗 Direct Access Official Website
Launch the tool online right now: https://html-viewer.org
Project Introduction
HTML Viewer is a lightweight browser-side front-end code editor and real-time preview runner, which solves the pain point of difficult cross-checking between source code and rendered page effect in daily front-end writing and learning.
Its most distinctive core capability is two-way synchronized highlighting between code editor and preview window: click a piece of code on the left, the matching element on the preview page will be marked; pick any content on the preview page, and the editor will instantly jump to and highlight the corresponding source code lines. This feature greatly speeds up error troubleshooting, element positioning and code comprehension, whether you are modifying page layout or learning how markup renders web pages.
Beyond code linkage lookup, the platform also supports direct visual editing on the preview panel. You can bold text, adjust font sizes, insert images and generate lists directly on the rendered page without manually typing HTML tags one by one. The system will automatically generate standard source code synchronously, which effectively reduces repetitive mechanical coding work and improves work efficiency for both developers and learners.
The whole tool requires no software download, no account registration, and all file parsing and preview rendering are completed locally in your browser, so your code content will not be uploaded to any external server, fully protecting your code privacy. It also supports local file import, one-click code formatting, syntax error repair and file export, forming a complete closed-loop workflow from importing materials to exporting finished files.
Suitable Crowd
Core Functional Details
1. Bidirectional Code-Preview Highlight & Mapping
2. WYSIWYG Visual Editing on Preview Side
Activate the visual edit button above the preview area to call up the formatting toolbar, supporting these operations directly on the rendered page:
3. Practical File & Code Auxiliary Tools
✅ Import local HTML/CSS/JS files from your device into the editor ✅ One-click code formatting to unify indentation and typesetting for disorganized code ✅ HTML syntax error detection and intelligent one-click repair ✅ Expand or collapse all code blocks to facilitate reading long nested documents ✅ Export the edited source file back to local storage for saving and delivery ✅ Toggle dark mode to reduce eye strain during long editing sessions ✅ Open preview page or source code page in a separate new browser tab
Project Preview Material
Screenshot 1: Two-way code highlighting demonstration
Screenshot 2: Preview area visual editing function display
Optional Demo Video
File name:
two-way-highlight-demo.mp4The video records the complete operation process of bidirectional highlighting linkage and preview-side visual editing, intuitively showing the core experience of the tool.Quick Start Guide
Privacy & Security Statement
All code analysis, page rendering and file processing are executed locally inside the user’s browser. The platform will not collect, upload or store any of your source code and file content, and will not transmit data to any third-party servers.
Open Source License
MIT License Free for personal learning, non-commercial use, secondary modification and open source distribution.