HTML attribute: step

Draft
This page is not complete.

Valid for the numeric input types, including the date, month, week, time, datetime-local, number and range types, the step attribute is a number that specifies the granularity that the value must adhere to or the keyword any.

The step sets the stepping interval when clicking up and down spinner buttons, moving a slider left and right on a range, and validating the different date types. If not explicitly included, step defaults to 1 for number and range, and 1 unit type (minute, week, month, day) for the date/time input types. The value can must be a positive number - integer or float -- or the special value any, which means no stepping is implied, and any value is allowed (barring other constraints, such as min and max).

The default stepping value for number inputs is 1, allowing only integers to be entered, unless the stepping base is not an integer. The default stepping value for time is 1 second, with 900 being equal to 15 minutes.

Default values for step
Input type Value Example
date 1 (day) <input type="date" min="2019-12-25" step="1">
month 1 (month) <input type="month" min="2019-12" step="12">
week 1 (week) <input type="week" min="2019-W23" step="2">
time 60 (seconds) <input type="time" min="09:00" step="900">
datetime-local 1 (day)

<input type="datetime-local" min="019-12-25T19:30" step="7">

number 1 <input type="number" min="0" step="0.1" max="10">
range 1 <input type="range" min="0" step="2" max="10">

If any is not explicity set, valid values for the number, date/time input types, and range input types are equal to the basis for stepping - the min value and increments of the step value, up to the max value, if specified. For example, if we have <input type="number" min="10" step="2"> any even integer, 10 or great, is valid. If omitted, <input type="number">, any integer is valid, but floats, like 4.2, are not valid, as step defaults to 1. For 4.2 to be valid, step would have had to be set to any, 0.1, 0.2, or any the min value would have had to be a number ending in .2, such as <input type="number" min="-5.2">

min impact on step

The value of min and step define what are valid values, even if the step attribute is not included, as step defaults to 0.

We add a big red border around invalid inputs:

input:invalid {
  border: solid red 3px;
}

Then define an input with a minimum value of 7.2, omitting the step attribute, wherein it defaults to 1.

<input id="myNumber" name="myNumber" type="number" step="2" min="1.2">

Valid values include 1.2, 3.2, 5.2, 7.2, 9.2, 11.2, and so on. Integers and even numbers follwed by .2 are not valid. As we included an invalid value, supporting browsers will show the value as invalid. The number spinner, if present, will only show valid float values of 1.2 and greater

Note: When the data entered by the user doesn't adhere to the stepping configuration, the value is considered invalid in contraint validation and will match the :invalid and :out-of-range pseudoclasses

See Client-side validation and stepMismatch for more information.

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'step attribute' in that specification.
Living Standard
HTML5
The definition of 'step attribute' in that specification.
Recommendation

Accessibility concerns

Provide instructions to help users understand how to complete the form and use individual form controls. Indicate any required and optional input, data formats, and other relevant information. When using the min attribute, ensure this minimum requirement is understood by the user. Providing instructions within the <label> may be sufficient. If providing instructions outside of labels, which allows more flexible positioning and design, consider using  aria-labelledby or aria-describedby.

See also