Replace Spaces & Underscores

Instantly convert spaces to underscores, hyphens, or custom delimiters. Perfect for URL slugs, filenames, and coding.

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Ultra Fast

Changes apply in real-time. No server delays or page reloads.

100% Private

Processing happens in your browser. Your data never leaves your device.

File Ready

Easily process large text files via drag-and-drop or file selector.

Try These Examples

Filename Cleanup

Convert a filename with spaces to underscores for web compatibility.

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URL Slugify

Turn a blog post title into a URL-friendly hyphenated slug.

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Underscore to Space

Restore underscored variable names back to readable text.

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Hyphen to Space

Convert hyphenated tags back to natural language.

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Why Replace Spaces with Underscores?

Converting spaces to underscores (or hyphens) is a common task for developers, content creators, and data analysts. This process is often called "slugifying" or "normalizing" text.

Common Use Cases

  • Filenames: Operating systems and web servers prefer filenames without spaces (e.g., my_vacation_photo.jpg).
  • URLs (Slugs): URLs cannot contain spaces. Converting "My Blog Post" to my-blog-post or my_blog_post makes it web-safe.
  • Programming Variables: Most programming languages (Python, C, PHP) do not allow spaces in variable names. user id becomes user_id (snake_case).
  • Data Cleaning: Standardizing data formats for database imports often requires replacing spaces with specific delimiters.

How to Use

  1. Enter Text: Paste your text into the input box or drag and drop a file.
  2. Select Mode: Choose whether you want to replace spaces with underscores, hyphens, or vice versa.
  3. Copy/Download: The text transforms instantly. Click "Copy Result" or "Download .txt" to save it.