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💯Go Struct and Field validation, including Cross Field, Cross Struct, Map, Slice and Array diving


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Package validator

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Package validator implements value validations for structs and individual fields based on tags.

It has the following unique features:

  • Cross Field and Cross Struct validations by using validation tags or custom validators.
  • Slice, Array and Map diving, which allows any or all levels of a multidimensional field to be validated.
  • Ability to dive into both map keys and values for validation
  • Handles type interface by determining it's underlying type prior to validation.
  • Handles custom field types such as sql driver Valuer see Valuer
  • Alias validation tags, which allows for mapping of several validations to a single tag for easier defining of validations on structs
  • Extraction of custom defined Field Name e.g. can specify to extract the JSON name while validating and have it available in the resulting FieldError
  • Customizable i18n aware error messages.
  • Default validator for the gin web framework; upgrading from v8 to v9 in gin see here


Use go get.

go get

Then import the validator package into your own code.

import ""

Error Return Value

Validation functions return type error

They return type error to avoid the issue discussed in the following, where err is always != nil:

Validator returns only InvalidValidationError for bad validation input, nil or ValidationErrors as type error; so, in your code all you need to do is check if the error returned is not nil, and if it's not check if error is InvalidValidationError ( if necessary, most of the time it isn't ) type cast it to type ValidationErrors like so:

err := validate.Struct(mystruct)
validationErrors := err.(validator.ValidationErrors)

Usage and documentation

Please see for detailed usage docs.


Baked-in Validations

Special Notes:

  • If new to using validator it is highly recommended to initialize it using the WithRequiredStructEnabled option which is opt-in to new behaviour that will become the default behaviour in v11+. See documentation for more details.
validate := validator.New(validator.WithRequiredStructEnabled())


Tag Description
eqcsfield Field Equals Another Field (relative)
eqfield Field Equals Another Field
fieldcontains Check the indicated characters are present in the Field
fieldexcludes Check the indicated characters are not present in the field
gtcsfield Field Greater Than Another Relative Field
gtecsfield Field Greater Than or Equal To Another Relative Field
gtefield Field Greater Than or Equal To Another Field
gtfield Field Greater Than Another Field
ltcsfield Less Than Another Relative Field
ltecsfield Less Than or Equal To Another Relative Field
ltefield Less Than or Equal To Another Field
ltfield Less Than Another Field
necsfield Field Does Not Equal Another Field (relative)
nefield Field Does Not Equal Another Field


Tag Description
cidr Classless Inter-Domain Routing CIDR
cidrv4 Classless Inter-Domain Routing CIDRv4
cidrv6 Classless Inter-Domain Routing CIDRv6
datauri Data URL
fqdn Full Qualified Domain Name (FQDN)
hostname Hostname RFC 952
hostname_port HostPort
hostname_rfc1123 Hostname RFC 1123
ip Internet Protocol Address IP
ip4_addr Internet Protocol Address IPv4
ip6_addr Internet Protocol Address IPv6
ip_addr Internet Protocol Address IP
ipv4 Internet Protocol Address IPv4
ipv6 Internet Protocol Address IPv6
mac Media Access Control Address MAC
tcp4_addr Transmission Control Protocol Address TCPv4
tcp6_addr Transmission Control Protocol Address TCPv6
tcp_addr Transmission Control Protocol Address TCP
udp4_addr User Datagram Protocol Address UDPv4
udp6_addr User Datagram Protocol Address UDPv6
udp_addr User Datagram Protocol Address UDP
unix_addr Unix domain socket end point Address
uri URI String
url URL String
http_url HTTP URL String
url_encoded URL Encoded
urn_rfc2141 Urn RFC 2141 String


Tag Description
alpha Alpha Only
alphanum Alphanumeric
alphanumunicode Alphanumeric Unicode
alphaunicode Alpha Unicode
ascii ASCII
boolean Boolean
contains Contains
containsany Contains Any
containsrune Contains Rune
endsnotwith Ends Not With
endswith Ends With
excludes Excludes
excludesall Excludes All
excludesrune Excludes Rune
lowercase Lowercase
multibyte Multi-Byte Characters
number Number
numeric Numeric
printascii Printable ASCII
startsnotwith Starts Not With
startswith Starts With
uppercase Uppercase


Tag Description
base64 Base64 String
base64url Base64URL String
base64rawurl Base64RawURL String
bic Business Identifier Code (ISO 9362)
bcp47_language_tag Language tag (BCP 47)
btc_addr Bitcoin Address
btc_addr_bech32 Bitcoin Bech32 Address (segwit)
credit_card Credit Card Number
mongodb MongoDB ObjectID
mongodb_connection_string MongoDB Connection String
cron Cron
spicedb SpiceDb ObjectID/Permission/Type
datetime Datetime
e164 e164 formatted phone number
email E-mail String
eth_addr Ethereum Address
hexadecimal Hexadecimal String
hexcolor Hexcolor String
hsl HSL String
hsla HSLA String
html HTML Tags
html_encoded HTML Encoded
isbn International Standard Book Number
isbn10 International Standard Book Number 10
isbn13 International Standard Book Number 13
issn International Standard Serial Number
iso3166_1_alpha2 Two-letter country code (ISO 3166-1 alpha-2)
iso3166_1_alpha3 Three-letter country code (ISO 3166-1 alpha-3)
iso3166_1_alpha_numeric Numeric country code (ISO 3166-1 numeric)
iso3166_2 Country subdivision code (ISO 3166-2)
iso4217 Currency code (ISO 4217)
json JSON
jwt JSON Web Token (JWT)
latitude Latitude
longitude Longitude
luhn_checksum Luhn Algorithm Checksum (for strings and (u)int)
postcode_iso3166_alpha2 Postcode
postcode_iso3166_alpha2_field Postcode
rgb RGB String
rgba RGBA String
ssn Social Security Number SSN
timezone Timezone
uuid Universally Unique Identifier UUID
uuid3 Universally Unique Identifier UUID v3
uuid3_rfc4122 Universally Unique Identifier UUID v3 RFC4122
uuid4 Universally Unique Identifier UUID v4
uuid4_rfc4122 Universally Unique Identifier UUID v4 RFC4122
uuid5 Universally Unique Identifier UUID v5
uuid5_rfc4122 Universally Unique Identifier UUID v5 RFC4122
uuid_rfc4122 Universally Unique Identifier UUID RFC4122
md4 MD4 hash
md5 MD5 hash
sha256 SHA256 hash
sha384 SHA384 hash
sha512 SHA512 hash
ripemd128 RIPEMD-128 hash
ripemd128 RIPEMD-160 hash
tiger128 TIGER128 hash
tiger160 TIGER160 hash
tiger192 TIGER192 hash
semver Semantic Versioning 2.0.0
ulid Universally Unique Lexicographically Sortable Identifier ULID
cve Common Vulnerabilities and Exposures Identifier (CVE id)


Tag Description
eq Equals
eq_ignore_case Equals ignoring case
gt Greater than
gte Greater than or equal
lt Less Than
lte Less Than or Equal
ne Not Equal
ne_ignore_case Not Equal ignoring case


Tag Description
dir Existing Directory
dirpath Directory Path
file Existing File
filepath File Path
image Image
isdefault Is Default
len Length
max Maximum
min Minimum
oneof One Of
required Required
required_if Required If
required_unless Required Unless
required_with Required With
required_with_all Required With All
required_without Required Without
required_without_all Required Without All
excluded_if Excluded If
excluded_unless Excluded Unless
excluded_with Excluded With
excluded_with_all Excluded With All
excluded_without Excluded Without
excluded_without_all Excluded Without All
unique Unique


Tag Description
iscolor hexcolor|rgb|rgba|hsl|hsla
country_code iso3166_1_alpha2|iso3166_1_alpha3|iso3166_1_alpha_numeric


Run on MacBook Pro (15-inch, 2017) go version go1.10.2 darwin/amd64
go version go1.21.0 darwin/arm64
goos: darwin
goarch: arm64
BenchmarkFieldSuccess-8                                         33142266                35.94 ns/op            0 B/op          0 allocs/op
BenchmarkFieldSuccessParallel-8                                 200816191                6.568 ns/op           0 B/op          0 allocs/op
BenchmarkFieldFailure-8                                          6779707               175.1 ns/op           200 B/op          4 allocs/op
BenchmarkFieldFailureParallel-8                                 11044147               108.4 ns/op           200 B/op          4 allocs/op
BenchmarkFieldArrayDiveSuccess-8                                 6054232               194.4 ns/op            97 B/op          5 allocs/op
BenchmarkFieldArrayDiveSuccessParallel-8                        12523388                94.07 ns/op           97 B/op          5 allocs/op
BenchmarkFieldArrayDiveFailure-8                                 3587043               334.3 ns/op           300 B/op         10 allocs/op
BenchmarkFieldArrayDiveFailureParallel-8                         5816665               200.8 ns/op           300 B/op         10 allocs/op
BenchmarkFieldMapDiveSuccess-8                                   2217910               540.1 ns/op           288 B/op         14 allocs/op
BenchmarkFieldMapDiveSuccessParallel-8                           4446698               258.7 ns/op           288 B/op         14 allocs/op
BenchmarkFieldMapDiveFailure-8                                   2392759               504.6 ns/op           376 B/op         13 allocs/op
BenchmarkFieldMapDiveFailureParallel-8                           4244199               286.9 ns/op           376 B/op         13 allocs/op
BenchmarkFieldMapDiveWithKeysSuccess-8                           2005857               592.1 ns/op           288 B/op         14 allocs/op
BenchmarkFieldMapDiveWithKeysSuccessParallel-8                   4400850               296.9 ns/op           288 B/op         14 allocs/op
BenchmarkFieldMapDiveWithKeysFailure-8                           1850227               643.8 ns/op           553 B/op         16 allocs/op
BenchmarkFieldMapDiveWithKeysFailureParallel-8                   3293233               375.1 ns/op           553 B/op         16 allocs/op
BenchmarkFieldCustomTypeSuccess-8                               12174412                98.25 ns/op           32 B/op          2 allocs/op
BenchmarkFieldCustomTypeSuccessParallel-8                       34389907                35.49 ns/op           32 B/op          2 allocs/op
BenchmarkFieldCustomTypeFailure-8                                7582524               156.6 ns/op           184 B/op          3 allocs/op
BenchmarkFieldCustomTypeFailureParallel-8                       13019902                92.79 ns/op          184 B/op          3 allocs/op
BenchmarkFieldOrTagSuccess-8                                     3427260               349.4 ns/op            16 B/op          1 allocs/op
BenchmarkFieldOrTagSuccessParallel-8                            15144128                81.25 ns/op           16 B/op          1 allocs/op
BenchmarkFieldOrTagFailure-8                                     5913546               201.9 ns/op           216 B/op          5 allocs/op
BenchmarkFieldOrTagFailureParallel-8                             9810212               113.7 ns/op           216 B/op          5 allocs/op
BenchmarkStructLevelValidationSuccess-8                         13456327                87.66 ns/op           16 B/op          1 allocs/op
BenchmarkStructLevelValidationSuccessParallel-8                 41818888                27.77 ns/op           16 B/op          1 allocs/op
BenchmarkStructLevelValidationFailure-8                          4166284               272.6 ns/op           264 B/op          7 allocs/op
BenchmarkStructLevelValidationFailureParallel-8                  7594581               152.1 ns/op           264 B/op          7 allocs/op
BenchmarkStructSimpleCustomTypeSuccess-8                         6508082               182.6 ns/op            32 B/op          2 allocs/op
BenchmarkStructSimpleCustomTypeSuccessParallel-8                23078605                54.78 ns/op           32 B/op          2 allocs/op
BenchmarkStructSimpleCustomTypeFailure-8                         3118352               381.0 ns/op           416 B/op          9 allocs/op
BenchmarkStructSimpleCustomTypeFailureParallel-8                 5300738               224.1 ns/op           432 B/op         10 allocs/op
BenchmarkStructFilteredSuccess-8                                 4761807               251.1 ns/op           216 B/op          5 allocs/op
BenchmarkStructFilteredSuccessParallel-8                         8792598               128.6 ns/op           216 B/op          5 allocs/op
BenchmarkStructFilteredFailure-8                                 5202573               232.1 ns/op           216 B/op          5 allocs/op
BenchmarkStructFilteredFailureParallel-8                         9591267               121.4 ns/op           216 B/op          5 allocs/op
BenchmarkStructPartialSuccess-8                                  5188512               231.6 ns/op           224 B/op          4 allocs/op
BenchmarkStructPartialSuccessParallel-8                          9179776               123.1 ns/op           224 B/op          4 allocs/op
BenchmarkStructPartialFailure-8                                  3071212               392.5 ns/op           440 B/op          9 allocs/op
BenchmarkStructPartialFailureParallel-8                          5344261               223.7 ns/op           440 B/op          9 allocs/op
BenchmarkStructExceptSuccess-8                                   3184230               375.0 ns/op           424 B/op          8 allocs/op
BenchmarkStructExceptSuccessParallel-8                          10090130               108.9 ns/op           208 B/op          3 allocs/op
BenchmarkStructExceptFailure-8                                   3347226               357.7 ns/op           424 B/op          8 allocs/op
BenchmarkStructExceptFailureParallel-8                           5654923               209.5 ns/op           424 B/op          8 allocs/op
BenchmarkStructSimpleCrossFieldSuccess-8                         5232265               229.1 ns/op            56 B/op          3 allocs/op
BenchmarkStructSimpleCrossFieldSuccessParallel-8                17436674                64.75 ns/op           56 B/op          3 allocs/op
BenchmarkStructSimpleCrossFieldFailure-8                         3128613               383.6 ns/op           272 B/op          8 allocs/op
BenchmarkStructSimpleCrossFieldFailureParallel-8                 6994113               168.8 ns/op           272 B/op          8 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldSuccess-8              3506487               340.9 ns/op            64 B/op          4 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldSuccessParallel-8     13431300                91.77 ns/op           64 B/op          4 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldFailure-8              2410566               500.9 ns/op           288 B/op          9 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldFailureParallel-8      6344510               188.2 ns/op           288 B/op          9 allocs/op
BenchmarkStructSimpleSuccess-8                                   8922726               133.8 ns/op             0 B/op          0 allocs/op
BenchmarkStructSimpleSuccessParallel-8                          55291153                23.63 ns/op            0 B/op          0 allocs/op
BenchmarkStructSimpleFailure-8                                   3171553               378.4 ns/op           416 B/op          9 allocs/op
BenchmarkStructSimpleFailureParallel-8                           5571692               212.0 ns/op           416 B/op          9 allocs/op
BenchmarkStructComplexSuccess-8                                  1683750               714.5 ns/op           224 B/op          5 allocs/op
BenchmarkStructComplexSuccessParallel-8                          4578046               257.0 ns/op           224 B/op          5 allocs/op
BenchmarkStructComplexFailure-8                                   481585              2547 ns/op            3041 B/op         48 allocs/op
BenchmarkStructComplexFailureParallel-8                           965764              1577 ns/op            3040 B/op         48 allocs/op
BenchmarkOneof-8                                                17380881                68.50 ns/op            0 B/op          0 allocs/op
BenchmarkOneofParallel-8                                         8084733               153.5 ns/op             0 B/op          0 allocs/op

Complementary Software

Here is a list of software that complements using this library either pre or post validation.

  • form - Decodes url.Values into Go value(s) and Encodes Go value(s) into url.Values. Dual Array and Full map support.
  • mold - A general library to help modify or set data within data structures and other objects

How to Contribute

Make a pull request...


Distributed under MIT License, please see license file within the code for more details.


This project has grown large enough that more than one person is required to properly support the community. If you are interested in becoming a maintainer please reach out to me