Character Limits
Show how much room is left before text gets rejected or cut off.
What it adds
Live remaining-character feedback on limited fields, counting the same way the server does.
What your agent is told to do
5
What your agent is told to do
5-
1
Find every field with a length limit — database column, API constraint, or downstream service — and surface that limit in the UI.
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2
Count the same units the server counts. If the server counts Unicode characters, do not count UTF-16 code units in the browser; the two disagree on emoji and the user gets rejected for text that looked fine.
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3
Show remaining count rather than used count once the field is near the limit, and change its emphasis at a threshold rather than colouring it from the start.
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4
Decide whether to hard-block typing past the limit or allow overflow with a clear error. Hard blocking silently eats pasted text, so prefer allowing overflow and blocking submission.
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5
Do NOT announce every keystroke to screen readers. Announce only when crossing the warning threshold and when going over.
Edge cases it handles
6
Edge cases it handles
6- Pasting text over the limit must keep the text and show the overage, not truncate it without telling anyone.
- Line breaks must count consistently between client and server, including CRLF versus LF.
- Composed emoji and combining characters must count as the user perceives them, or the rule must be stated.
- Trailing whitespace trimmed by the server must be trimmed by the counter too.
- A field starting over the limit — imported or legacy data — must show the state clearly and still be editable.
- Colour alone must not carry the warning.
Definition of done
8
Definition of done
8- Every length-limited field shows its limit and remaining count.
- The client counts identically to the server, including emoji and line breaks.
- Pasted overflow is preserved and reported rather than silently truncated.
- Threshold and over-limit states are announced once, not on every keystroke.
- The over-limit state is conveyed by more than colour.
- Submission is blocked with a clear message when over the limit.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
Unit Converter
Unit Converter
Let people convert a value between units without leaving the page they are on.
What it does
An inline converter that takes a typed value in one unit and shows the equivalent in another, in place.
How it works
- 1 Start from the units the app actually deals in. A shipping tool needs weight and length; a recipe tool needs volume and temperature. Ship those and leave the rest out.
- 2 Convert as the user types, with the result visible beside the input rather than behind a submit button. Let either side be edited so the conversion runs in both directions.
- 3 Reuse the app's existing number parsing and display formatting rather than writing new ones. If Locale-Aware Numbers and Dates or Number Formatting Component is already present, the converter must render through it so grouping and decimal marks match the rest of the app.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/unit-converter
Field State Matrix
Field State Matrix
Decide once how every field looks and behaves in every state, before screens improvise.
What it does
A defined and documented set of visual and behavioural states covering every input type in the app.
How it works
- 1 Enumerate the app's input types and cross them against every state they can enter: empty, filled, focused, hovered, invalid, valid, disabled, read-only, loading, and browser-autofilled.
- 2 Define disabled and read-only as genuinely different states — a read-only field shows a real value the user may select and copy, a disabled field is inert and excluded from submission.
- 3 Define the loading state so the field is visibly busy and not editable, and say what happens to a keystroke that arrives mid-load rather than letting it be silently swallowed.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/field-state-matrix
Required Field Indicator
Required Field Indicator
Make it obvious which fields must be filled in and which may be left alone.
What it does
A consistent marking of required and optional fields across every form in the app.
How it works
- 1 Count the required and optional fields across the app's forms and pick the convention that marks the minority — if most fields are required, mark the optional ones instead.
- 2 Apply the chosen convention to every form without exception, and state the convention once at the top of each form so the marker means something to a first-time reader.
- 3 Expose the requirement to assistive technology as well as visually, so the control itself reports that it is required rather than relying on a symbol beside the label.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/required-field-indicator
How it works
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1
Copy the link
Grab the Markdown instruction URL for this feature.
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2
Give it to your AI
Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
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3
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.