Validationflags: i

MIME Type

Validate MIME media type strings like text/html, application/json, or image/png; charset=utf-8.

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("^([a-z]+)\\/([a-z0-9][a-z0-9!#$&\\-^_.]*)(?:;\\s*[a-z]+=\\S+)*$", "i");
const input = "application/json";
const matches = [...input.matchAll(re)];
console.log(matches.map(m => m[0]));

Uses `String.prototype.matchAll` for global iteration (Node 12+ / all modern browsers).

Python (re) code

pyPython

import re

pattern = re.compile(r"^([a-z]+)\/([a-z0-9][a-z0-9!#$&\-^_.]*)(?:;\s*[a-z]+=\S+)*$", re.IGNORECASE)
input_text = "application/json"
for m in pattern.finditer(input_text):
    print(m.group(0))

Stdlib `re` module — no third-party dependency. Works on Python 3.6+.

Go (RE2) code

goGo

package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`(?i)^([a-z]+)\/([a-z0-9][a-z0-9!#$&\-^_.]*)(?:;\s*[a-z]+=\S+)*$`)
	input := `application/json`
	for _, match := range re.FindAllString(input, -1) {
		fmt.Println(match)
	}
}

Uses `regexp.MustCompile` (panics on bad patterns at startup) and `FindAllString` for all matches.

Pattern

regexengine-agnostic

^([a-z]+)\/([a-z0-9][a-z0-9!#$&\-^_.]*)(?:;\s*[a-z]+=\S+)*$   (flags: i)

Raw source: ^([a-z]+)\/([a-z0-9][a-z0-9!#$&\-^_.]*)(?:;\s*[a-z]+=\S+)*$

How it works

Group 1 captures the primary type (text, image, application, etc). Group 2 captures the subtype using the allowed MIME subtype character set. The optional trailing group (?:;\s*[a-z]+=\S+)* matches parameters like charset=utf-8 or boundary=something.