Prefix Lines Tool — Add Text Before Every Line

Complete Guide to the Prefix Lines Tool

What Is the Prefix Lines Tool?

The Prefix Lines tool is a free online utility designed to add any custom text, number, or symbol before every line of a given block of text. Whether you are preparing a bulleted list, numbering items for a document, adding programming comments, or formatting data for import into a spreadsheet, this tool handles the repetitive work for you in a single click. Instead of manually typing the same prefix hundreds of times, you simply paste your content, specify the prefix, and get instant results.

Key Features That Make This Tool Stand Out

ToolGalaxy's Prefix Lines tool is built with real-world productivity in mind. Here are the core features that differentiate it from basic text editors:

• Custom Prefix Input: Add any text string — bullets (•), dashes (—), arrows (→), hashtags (#), timestamps, or full words like "TODO:" or "ERROR:" — before every line.
• Sequential Numbering Mode: Automatically number each line with formats like "1. ", "1) ", "[1] ", or plain numbers. You control the starting number and step increment.
• Separator Control: Define exactly what comes between the prefix and the original line content — a space, a dash, a colon, or nothing at all.
• Skip Empty Lines: Optionally ignore blank lines so your output stays clean and properly formatted without unnecessary prefixes on empty rows.
• Trim Whitespace: Remove leading and trailing spaces from each line before applying the prefix, ensuring consistent formatting.
• Remove Existing Prefix: Strip previously added prefixes before applying new ones — perfect for reformatting lists that already have numbering or bullets.
• Live Mode: Enable real-time processing so the output updates as you type, giving you instant visual feedback without pressing any button.
• Swap Function: Move the output back into the input field to chain multiple operations — for example, add a prefix and then add a suffix in a second pass.
• Download as .txt: Export your processed text directly as a downloadable text file for offline use.

Common Use Cases

Developers frequently use this tool to add comment markers (//, #, --) before code lines for quick commenting or uncommenting. Content creators use it to convert plain text into bulleted or numbered lists for blog posts and presentations. Data analysts use it to add category labels or identifiers before CSV rows. Students use it to number study notes or quiz questions. Social media managers use it to add hashtags or emojis before each line of a post. The applications are virtually limitless — anywhere you need consistent text prepended to multiple lines, this tool saves significant time.

Privacy and Performance

All text processing happens entirely within your web browser using client-side JavaScript. Your data is never transmitted to any external server, stored in any database, or shared with any third party. This makes the tool safe for processing sensitive information such as proprietary code snippets, personal notes, or confidential business data. The tool loads instantly with zero server dependencies, ensuring fast performance even on slow internet connections. It works on all modern browsers including Chrome, Firefox, Safari, and Edge, and is fully responsive for use on smartphones and tablets.

Tips for Best Results

For cleanest output, ensure each item in your input is on its own line. Use the "Trim Whitespace" option if your source text has inconsistent spacing. If you are reformatting an existing list, enable "Remove Existing Prefix" first to strip old markers before applying new ones. When using sequential numbering with a custom prefix like "Item ", set the separator to a space or dash for readability. The live mode is ideal for short texts where you want to experiment with different prefixes quickly.