kumo.file_type.from_bytes

local ft = kumo.file_type.from_bytes(BYTES)

Since: Version 2025.12.02-67ee9e96

The functionality described in this section requires version 2025.12.02-67ee9e96 of KumoMTA, or a more recent version.

Attempts to determine the file type from the provided string, which may also be binary bytes.

This function will always succeed in returning a guess, which may or may not be accurate.

The return value is a FileTypeResult

local kumo = require 'kumo'
local utils = require 'policy-extras.policy_utils'

local ft = kumo.file_type.from_bytes '\xCA\xFE\xBA\xBE'
utils.assert_eq(ft, {
  name = 'Java class file',
  extensions = { 'class' },
  media_types = {
    'application/java',
    'application/java-byte-code',
    'application/java-vm',
    'application/x-httpd-java',
    'application/x-java',
    'application/x-java-class',
    'application/x-java-vm',
  },
})