diff --git a/internal/domain/pkce.go b/internal/domain/pkce.go
deleted file mode 100644
index 89b471c..0000000
--- a/internal/domain/pkce.go
+++ /dev/null
@@ -1,58 +0,0 @@
-//nolint: gosec
-package domain
-
-import (
-	"crypto/md5"
-	"crypto/sha1"
-	"crypto/sha256"
-	"crypto/sha512"
-	"encoding/base64"
-	"hash"
-	"io"
-)
-
-type (
-	PKCE struct {
-		Method    PKCEMethod
-		Verifier  string
-		Challenge string
-	}
-
-	PKCEMethod string
-)
-
-const (
-	PKCEMethodMD5   PKCEMethod = "MD5"
-	PKCEMethodPlain PKCEMethod = "plain"
-	PKCEMethodS1    PKCEMethod = "S1"
-	PKCEMethodS256  PKCEMethod = "S256"
-	PKCEMethodS512  PKCEMethod = "S512"
-)
-
-func (pkce PKCE) IsValid() bool {
-	h := pkce.Method.Hash()
-	if h == nil { // NOTE(toby3d): PLAIN
-		return pkce.Challenge == pkce.Verifier
-	}
-
-	_, _ = io.WriteString(h, pkce.Verifier)
-
-	return pkce.Challenge == base64.RawURLEncoding.EncodeToString(h.Sum(nil))
-}
-
-func (m PKCEMethod) Hash() hash.Hash {
-	switch m {
-	case PKCEMethodMD5:
-		return md5.New()
-	case PKCEMethodS1:
-		return sha1.New()
-	case PKCEMethodS256:
-		return sha256.New()
-	case PKCEMethodS512:
-		return sha512.New()
-	case PKCEMethodPlain:
-		fallthrough
-	default:
-		return nil
-	}
-}
diff --git a/internal/domain/pkce_test.go b/internal/domain/pkce_test.go
deleted file mode 100644
index 7b88c4c..0000000
--- a/internal/domain/pkce_test.go
+++ /dev/null
@@ -1,73 +0,0 @@
-package domain_test
-
-import (
-	"encoding/base64"
-	"io"
-	"math/rand"
-	"testing"
-	"time"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-
-	"source.toby3d.me/website/oauth/internal/domain"
-	"source.toby3d.me/website/oauth/internal/random"
-)
-
-const (
-	MinLength int = 42
-	MaxLength int = 128
-)
-
-func TestPKCEIsValid(t *testing.T) {
-	t.Parallel()
-
-	rand.Seed(time.Now().UnixNano())
-
-	//nolint: gosec
-	verifier := random.New().String(MinLength + rand.Intn(MaxLength-MinLength))
-
-	for _, testCase := range []struct {
-		Name   string
-		Method domain.PKCEMethod
-	}{{
-		Name:   "MD5",
-		Method: domain.PKCEMethodMD5,
-	}, {
-		Name:   "plain",
-		Method: domain.PKCEMethodPlain,
-	}, {
-		Name:   "S1",
-		Method: domain.PKCEMethodS1,
-	}, {
-		Name:   "S256",
-		Method: domain.PKCEMethodS256,
-	}, {
-		Name:   "S512",
-		Method: domain.PKCEMethodS512,
-	}, {
-		Name:   "fallback to plain",
-		Method: "UNDEFINED",
-	}} {
-		testCase := testCase
-
-		t.Run(testCase.Name, func(t *testing.T) {
-			t.Parallel()
-
-			pkce := &domain.PKCE{
-				Method:    testCase.Method,
-				Verifier:  verifier,
-				Challenge: verifier,
-			}
-
-			if h := pkce.Method.Hash(); h != nil {
-				_, err := io.WriteString(h, pkce.Verifier)
-				require.NoError(t, err)
-
-				pkce.Challenge = base64.RawURLEncoding.EncodeToString(h.Sum(nil))
-			}
-
-			assert.True(t, pkce.IsValid())
-		})
-	}
-}