Bug 284363 – <input type="number"> does not support full-width numbers (e.g., "ー２００") for Japanese IME users

• Component: Forms
• Status: NEW

[Kyouhei Horizumi]

When entering full-width numbers in an `<input type="number">` field and pressing Enter, the entered value disappears.
Unlike Firefox, Webkit-based browsers do not support full-width number input. This results in complaints from some Japanese users, especially those unfamiliar with input limitations, as they are unable to input numbers.
Safari should allow full-width number input, similar to Firefox.

## Reproduction Steps:

1. Create an `<input type="number">` field.
2. Try entering the value `ー２００` (a full-width number).

## Expected Behavior:

The browser should accept full-width numbers as valid input and convert them to their half-width equivalents when necessary, similar to Firefox.

## Actual Behavior:

### Safari:
Input value: ー２００ (input allowed, but invalid)  
.value: "" 
.valueAsNumber: NaN  

### Firefox:
Input value: ー２００ (input allowed, valid)    
.value: "-200"  
.valueAsNumber: -200  

### Chrome:
Input value: ー２００ (unable to input)  
.value: ""  
.valueAsNumber: NaN

## Environment:

+ Safari Technology Preview Release 209 (Safari 18.2, Webkit 20621.1.6) (macOS 15)
+ Firefox 133.0 (Windows 11)
+ Chrome 131.0.6778.109 (Windows 11)

## Reference

https://issuetracker.google.com/issues/383232110

[Radar WebKit Bug Importer]

<rdar://problem/141257181>

[Kyouhei Horizumi]

Sorry,
I initially wrote that when entering full-width numbers in an <input type="number"> field and pressing Enter, the entered value disappears. 
However, I need to correct this: that behavior occurs in Chrome.
In WebKit, the value does not disappear when pressing Enter but is internally treated as empty.

[Karl Dubost]

Created attachment 473601 [details]
testcase

This is a testcase to quickly try the issue for someone.

[Anne van Kesteren]

See also bug 250535. We're generally pretty strict at the moment for end user input, which isn't ideal.