A Go module to validate CNPJ numbers (Brazilian companies' unique identifier for the Federal Revenue).
Important
Starting in July 2026 the CNPJ number will be alphanumeric. This package already supports the new format. If you do not want to support the new format, tag this package to v0.1.1.
package main
import "github.com/cuducos/go-cnpj"
func main() {
// these return true
cnpj.IsValid("11222333000181")
cnpj.IsValid("11.222.333/0001-81")
cnpj.IsValid("12.ABC.345/01DE-35")
cnpj.IsValid("12ABC34501DE35")
// these return false
cnpj.IsValid("11.111.111/1111-11")
cnpj.IsValid("12.345.678 9012-34")
cnpj.IsValid("AB.CDE.FGH/IJKL-MN")
cnpj.IsValid("123")
// these return 11111111111111 and 12ABC34501DE35
cnpj.Unmask("11.111.111/1111-11")
cnpj.Unmask("12.ABC.345/01DE-35")
// these return 11.111.111/1111-11 and 12.ABC.345/01DE-35
cnpj.Mask("11111111111111")
cnpj.Mask("12ABC34501DE35")
}Based on Go CPF ❤️