Replace Spaces & Underscores

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

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ReadOnly Mode

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

URL Friendly

Convert spaces to underscores for filenames or URLs.

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Readable Variable

Convert database columns to readable text.

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SEO Slugs

Convert titles to hyphenated URL slugs.

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Clean Text

Remove hyphens to restore natural reading.

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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.