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CO-STAR Extension

Structures your ChatGPT prompts using Singapore GovTech's CO-STAR framework instead of freeform text.

Checked 5 Oct 2026 Reviewed by Alex Listed since October 2024

Screenshot of CO-STAR Extension

At a glance

Starts at Free Listed as free on the Chrome Web Store.
Free tier Yes
Platforms Chrome
Best for People wanting a structured framework for ChatGPT prompts
Not for Anyone comfortable freeform prompting without a fixed structure

5.0 out of 5

Scored by Alex after real use

Our verdict

CO-STAR Extension takes the CO-STAR prompt framework built by Singapore's GovTech and turns filled-in fields into a formatted ChatGPT prompt, with a real-time preview before you send it. People who want a repeatable structure rather than guessing at prompt wording each time will get the most out of it. Locking prompts into one fixed framework means it won't suit every kind of request.

✓What it does well

Structured prompt frameworkApplies the CO-STAR framework to structure prompts consistently.
Real-time previewShows a live preview of the formatted prompt before sending.
Chrome integrationIntegrates directly into the Chrome toolbar for quick access.

✕Where it falls short

One fixed frameworkLocks prompts into a single framework, not flexible formats.
ChatGPT focusedIs built only around ChatGPT, not other AI chat tools.
Manual field fillingRequires filling in each CO-STAR field by hand.

Key features

CO-STAR fieldsProvides input fields for each part of the CO-STAR framework.
Auto-formattingFormats entered text into a structured prompt automatically.
Live previewPreviews the finished prompt in real time as you type.
Toolbar accessOpens directly from the Chrome toolbar icon.

Questions about CO-STAR Extension

What does CO-STAR Extension do?

CO-STAR Extension structures ChatGPT prompts using the CO-STAR framework built by Singapore's GovTech, instead of freeform text. It provides an input field for each part of the framework, formats the entered text into a structured prompt, and shows a real-time preview before the prompt is sent.

Is CO-STAR Extension free?

CO-STAR Extension is free and listed as free on the Chrome Web Store, with no paid plan listed. It runs in Chrome and opens directly from the Chrome toolbar icon for quick access.

Does CO-STAR Extension work with AI tools other than ChatGPT?

No. CO-STAR Extension is built only around ChatGPT, not other AI chat tools, according to the reviewer. It also locks prompts into one fixed framework rather than flexible formats, and each CO-STAR field has to be filled in by hand.

Who should use CO-STAR Extension?

Toolio lists CO-STAR Extension as best for people who want a structured framework for ChatGPT prompts rather than guessing at wording each time. It is not for anyone comfortable with freeform prompting without a fixed structure.

How does Toolio score CO-STAR Extension?

CO-STAR Extension holds a Toolio score of 5.0 out of 5, given by Alex after real use on 5 Oct 2026. The reviewer credits its structured prompt framework, real-time preview and Chrome integration, while noting that one fixed framework will not suit every kind of request.

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