inputlength

Inputlength, or input length, is the measure of the size of a user's input in a given context. It is usually expressed as the number of characters or bytes and is a fundamental constraint in input validation and data storage.

In software systems, input length can be counted at different points and in different ways. Characters may be counted as code points, grapheme clusters, or code units, depending on the encoding and the level of processing. Unicode introduces complexities such as surrogate pairs and combining marks that can affect perceived length.

Language and platform specifics vary. In JavaScript, the string length property returns the number of UTF-16 code units rather than code points. In Python 3, len(str) yields Unicode code points. In C, strlen counts bytes until the NUL terminator. Databases often constrain length with VARCHAR(n) or similar definitions.

Web forms commonly use client-side limits via maxlength, but server-side validation is essential because client constraints can be bypassed. Length limits help prevent excessive resource use and certain attacks, but they should reflect storage and business rules and consider multi-byte encodings.

Best practices include validating length on the server, documenting constraints in the data model, and choosing counting methods appropriate for the user experience (for example, counting grapheme clusters for user-visible length). Always treat length as part of a broader input-validation strategy.