Prompt Variable Replacer

What Is the Prompt Variable Replacer?

The Prompt Variable Replacer is a fill-in-the-blanks editor for prompt templates. You write a prompt once, mark the parts that change with double curly braces such as {{role}}, {{topic}} or {{length}}, and the tool finds every placeholder, gives you a field for each one, and shows the finished prompt updating live as you type. It is the fastest way to turn one good prompt into a prompt you can reuse every day.

Everything happens inside your browser. The template, your values and your saved presets never leave the device, and the tool makes no network requests at all. That makes it safe for internal prompts, client briefs and anything else you would rather not paste into a web service.

Why You Would Use It

Most people who use language models regularly end up with a folder of near-identical prompts: the same structure, but the role, the audience, the word count or the product name changes every time. Editing those by hand is slow and easy to get wrong, and forgetting to replace one placeholder means the model receives literal braces instead of your instruction.

This tool is for content teams that run the same outline prompt across many articles, developers who keep a code review prompt and swap the file path, support leads who reuse a reply template with a different product name, teachers who change the topic and the reading level, and anyone maintaining a prompt library. The fill progress bar tells you at a glance whether the prompt is complete before you copy it.

How This Tool Works

The page has three numbered sections. In section one you choose a template: paste your own, or pick one of four ready-made samples (Marketing writer, Technical writer, Blog repurposing, Code review). Each sample ships with example values, so a single click gives you a working demo. Your template sits in a monospace editor where placeholders are highlighted as you type: amber while empty, green once they have a value.

The tool scans the template for patterns written as two curly braces around a name. Only letters, digits and underscores are accepted, and the name must start with a letter or an underscore. Anything else is reported in a warning box under the editor: an empty pair of braces, a name with a space or a hyphen, a closing pair with no opening pair, and a count of unclosed braces. Each placeholder appears in section two as a chip with its usage count, so a variable used three times is filled once and replaced in all three places.

Click a chip to edit its value inline. Enter saves, Escape cancels, and clicking away saves as well. Filled chips turn green and empty ones stay amber, and the progress bar and the filled counter above the section track completion. You can also fill everything at once, shuffle the values that are already filled, or open Bulk paste and type one name=value pair per line; only names that exist in your template are applied and the feedback line tells you how many landed.

Section three shows the result with every filled value highlighted in green and every still empty placeholder in amber. Copy puts the finished text on the clipboard, Copy raw template copies the original with the braces intact, and Save downloads the result as a prompt.txt file. The Drop empty placeholders switch removes unfinished placeholders from the output instead of leaving the braces visible, and the badge flips to Ready to copy when every placeholder is filled or that switch is on. Counts for tokens, characters, words and filled placeholders sit next to the badge.

Key Features

• Automatic detection of {{name}} placeholders with per variable usage counts
• Four ready-made sample templates plus your own pasted template
• Inline editing on chips with Enter to save and Escape to cancel
• Fill all with sample, Shuffle values, Bulk paste and Clear values
• Undo right after clearing, so a misclick is not the end of the world
• Warning box for empty, invalid or unbalanced placeholders
• Live output with green and amber highlighting and a fill progress bar
• Drop empty placeholders switch, token and character counters
• Named presets that save and reload templates, stored in the browser
• Copy, Copy raw template, Save as .txt and Ctrl/Cmd+Enter to copy

How to Use the Tool

1. Choose a template in section one. Click a sample card to load it, or click Paste your own and paste or type your template with {{placeholders}} in it.
2. Read the warning box if it appears and fix any placeholder the tool cannot parse.
3. In section two, click each chip and type the value. Press Enter to save. Use Fill all with sample for a quick demo or Bulk paste when you already have a list of name=value lines.
4. Watch the progress bar until it reads fully filled, then check section three.
5. Turn on Drop empty placeholders only if you intentionally want unfinished variables removed from the output.
6. Press Copy, Copy raw template or Save. Optional: type a preset name next to the template and press the bookmark button to save the template for later.

Limits and Rules

A placeholder counts only when it is written as double curly braces around a name made of letters, digits and underscores that starts with a letter or an underscore. Spaces, hyphens, dots and empty braces are not valid names and are flagged as warnings rather than being replaced.

Values are inserted exactly as you type them; the tool does not escape, quote or rewrite them, and it does not check whether the value makes sense. A template with no placeholders shows an empty state with a Load sample button. Presets store the template text only, not your values, and both templates and values live in local storage on this device, so clearing site data removes them. There is no size limit, no rate limit and no captcha because no request is made.

When to Use It and When Not to

Use it when the same prompt runs many times with a few changed words, when you want to see exactly what the model will receive, when you are handing a template to a colleague who should fill it themselves, or when you need to confirm that no literal placeholder slipped through.

Do not use it to build prompt logic. There are no conditionals, loops or defaults: an empty variable stays empty or disappears if you drop it. It is also the wrong tool for one-off prompts with no repeated parts, and it will not fetch values from a spreadsheet or an API; bulk paste is the only batch input.