Markdown Editor with Preview
Write Markdown and see exactly how it will render.
What it adds
A source editor paired with a live preview, where the stored value stays raw Markdown and the rendered HTML is sanitised.
What your agent is told to do
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What your agent is told to do
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Store the raw Markdown byte-for-byte. Never round-trip it through a rendered form and back — that silently rewrites people's spacing, list markers and escapes.
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Pick one Markdown flavour and one extension set, and use the same one on the client preview and the server renderer. A preview that disagrees with the published page is worse than no preview.
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Sanitise the generated HTML on the server before it is stored or served, including raw HTML blocks embedded in the source.
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Synchronise preview scroll to the editor loosely, anchored on block boundaries. Do not chase the caret.
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This is not a WYSIWYG surface. Toolbars that produce formatting directly and pasted-HTML cleanup are owned by Rich Text Editor; extend that rather than building a second editor here.
Edge cases it handles
6
Edge cases it handles
6- Fenced code blocks must render literally, including anything inside them that looks like Markdown or HTML.
- Raw HTML in the source must either be sanitised or disabled outright — decide and say which.
- Link and image URLs need scheme checks; a Markdown link is still a link.
- Scroll sync must not fight the user when they scroll the preview themselves.
- Very long documents must not re-render the whole preview on every keystroke — debounce it.
- Unsupported syntax must show as plain text, not silently vanish.
Definition of done
8
Definition of done
8- The stored value is the exact Markdown the user typed.
- Client preview and server render produce the same output for the same source.
- Generated HTML is sanitised server-side, including embedded raw HTML.
- Code fences render their contents literally.
- Scroll sync tracks the editor without jumping or hijacking manual preview scrolling.
- Preview rendering is debounced and stays responsive on long documents.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
Help Text Pattern
Help Text Pattern
Put field guidance in one predictable place, phrased the same way every time.
What it does
A consistent treatment for the short explanatory text that sits with a field and its control.
How it works
- 1 Collect the guidance the app currently scatters across placeholders, tooltips, asterisked footnotes, and modal help, and move it into one slot beneath the field.
- 2 Keep guidance that is required to complete the field permanently visible. A format rule hidden behind a hover target is not available to a touch user or a keyboard user.
- 3 Write help as the rule the user needs before typing — the accepted format, the consequence of the choice — not as a restatement of the label.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/help-text-pattern
Voice Dictation
Voice Dictation
Put a microphone in text fields so people can speak their input instead of typing it.
What it does
A dictation control on the app's longer text inputs that transcribes speech into the field as the user talks.
How it works
- 1 Add the control to the fields where typing is genuinely tedious: long descriptions, notes, comments, and message bodies. A microphone on a postcode field is clutter.
- 2 Show interim results in the field as they arrive, visually distinct from committed text, so the speaker can see it is working and correct course before they finish.
- 3 Reuse the app's existing Voice Transcription for the server-side path so one recognition configuration and one set of language settings serve both dictation and recorded audio.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/voice-dictation
Form Section Pattern
Form Section Pattern
Break long forms into labelled sections people can scan instead of read.
What it does
A section pattern grouping related fields under a heading, a description, and its own actions.
How it works
- 1 Find the forms that have grown past a screenful — settings, profiles, checkout, configuration — and group their fields by the question each group answers, not by the table the columns come from.
- 2 Give each section a heading in the document's heading order and an optional one-line description, so screen reader and keyboard users can jump between sections.
- 3 Allow at most one level of nesting. A section inside a section inside a tab gives the user no orientation and pushes the fields into a narrow gutter.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/form-section-pattern
How it works
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Copy the link
Grab the Markdown instruction URL for this feature.
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Give it to your AI
Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
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It inspects, then implements
Your agent reads your existing app first, then adds the feature to fit it.
Works with your stack
These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.
Need it tighter than that? Customize the feature and tell it exactly what you're running.