min/max/step Number Input Semantics

Checks parsed number-input min/max and step constraints using exact decimal arithmetic on the canonical decimal spelling of supplied finite numbers. Supply normalized positive step (default 1) and attribute presence flags; this is an ideal decimal model, independent of browser binary floating point tolerances.

Description

Number input constraints combine range bounds with an arithmetic step grid.

Number input constraints combine range bounds with an arithmetic step grid. The step base comes from min first, then the value attribute, then zero.^[1]

When to use min/max/step Number Input Semantics

Use this for the following task: Checks parsed number-input min/max and step constraints using exact decimal arithmetic on the canonical decimal spelling of supplied finite numbers. Supply normalized positive step (default 1) and attribute presence flags; this is an ideal decimal model, independent of browser binary floating point tolerances.

Prepare the parsed attribute values, element states or ordered local lists requested below. Keep attribute presence separate from value.

How to use min/max/step Number Input Semantics and understand its results

Prepare the parsed attribute values, element states or ordered local lists requested below. Keep attribute presence separate from value.
Enter value, hasMin, min, hasMax, max, stepAny, step, hasValueAttribute, valueAttribute using the field table, then run the tool.
Read rangeUnderflow, rangeOverflow, stepMismatch, stepBase. Interpret flags, units, ordering and placeholder values using the rules below.
Review any reported issue or failed check, correct the supplied values when appropriate, and verify the result in its intended context.

Input field	Meaning	Value type and bounds	Requirement
value	Value	number	Required
hasMin	Has Min	boolean	Required
min	Min	number	Required
hasMax	Has Max	boolean	Required
max	Max	number	Required
stepAny	Step Any	boolean	Required
step	Step	number; minimum 0	Required
hasValueAttribute	Has Value Attribute	boolean	Required
valueAttribute	Value Attribute	number	Required

Supply finite parsed numbers, normalized positive step and attribute-presence flags. Convert canonical decimal spellings into scaled integers for exact step divisibility. Range checks use only present min/max.^[2]

stepMismatch = !stepAny AND (value − stepBase) is not an integer multiple of step

This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.

Output field	Meaning	Value type
rangeUnderflow	Range Underflow	boolean
rangeOverflow	Range Overflow	boolean
stepMismatch	Step Mismatch	boolean
stepBase	Step Base	number

json

{
  "input": {
    "value": 0.3,
    "hasMin": true,
    "min": 0.1,
    "hasMax": true,
    "max": 1,
    "stepAny": false,
    "step": 0.2,
    "hasValueAttribute": false,
    "valueAttribute": 0
  },
  "output": {
    "rangeUnderflow": false,
    "rangeOverflow": false,
    "stepMismatch": false,
    "stepBase": 0.1
  }
}

Limitations and assumptions

This is an ideal decimal model; browser floating-point tolerances can differ. A positive step remains required even with stepAny true.

This evaluates supplied local information; it does not fetch a page or run a browser. Malformed requests produce input errors. A successfully evaluated request can still contain false flags, empty result lists or a result outside the supplied threshold; those outcomes have the meanings stated above.

Alternative or Complementary methods

Choose required/readonly/disabled Diff Table for this operation: Resolves required, readonly and disabled flags for an ordinary input type. Effective disabled includes inherited fieldset state supplied by the caller. Submission eligibility concerns disabling only; name, checkedness and submitter selection are separate. For a complementary task, use textarea/input maxlength Parity for this operation: Measures an input or textarea API value in UTF-16 code units against maxlength. Supply the already-normalized API value; this does not model user-edit constraint-validation conditions or grapheme counts.

Further background: HTML / accessibility reference: min/max/step Number Input Semantics.

References

HTML / accessibility reference: min/max/step Number Input Semantics — WHATWG
min/max/step Number Input Semantics — tool.io

Similar or alternative tools

required/readonly/disabled Diff Table
Resolves required, readonly and disabled flags for an ordinary input type. Effective disabled includes inherited fieldset state supplied by the caller. Submission eligibility concerns disabling only; name, checkedness and submitter selection are separate.
textarea/input maxlength Parity
Measures an input or textarea API value in UTF-16 code units against maxlength. Supply the already-normalized API value; this does not model user-edit constraint-validation conditions or grapheme counts.