diff --git a/TODO.md b/TODO.md
index 404abd1..be3eb08 100644
--- a/TODO.md
+++ b/TODO.md
@@ -29,6 +29,11 @@ P2: security: referer blacklist
 
 # Completed Steps
 
+- 2026-10-04 dead code in `internal/imgcache` is gone (closes #73): `Purge`,
+  which only returned an error and which nothing called, is no longer part of
+  the `ImageCache` interface or `Service`; the `SignatureValidator`,
+  `Allowlist` and `Storage` interfaces, which nothing implemented or used, are
+  deleted. Nothing else changes.
 - 2026-10-04 upstream host semaphores and variant `.meta` files no longer
   outlive their use (closes #87): the fetcher counts the fetches holding or
   waiting for a slot of each upstream host's semaphore and removes the host's
diff --git a/internal/imgcache/imgcache.go b/internal/imgcache/imgcache.go
index a74e783..1647658 100644
--- a/internal/imgcache/imgcache.go
+++ b/internal/imgcache/imgcache.go
@@ -5,7 +5,6 @@ import (
 	"context"
 	"errors"
 	"io"
-	"net/url"
 	"time"
 )
 
@@ -154,9 +153,6 @@ type ImageCache interface {
 	// Warm pre-fetches and caches an image without returning it
 	Warm(ctx context.Context, req *ImageRequest) error
 
-	// Purge removes a cached image
-	Purge(ctx context.Context, req *ImageRequest) error
-
 	// Stats returns cache statistics
 	Stats(ctx context.Context) (*CacheStats, error)
 }
@@ -176,29 +172,3 @@ type CacheStats struct {
 	// HitRate is HitCount / (HitCount + MissCount)
 	HitRate float64
 }
-
-// SignatureValidator validates request signatures
-type SignatureValidator interface {
-	// Validate checks if the signature is valid for the request
-	Validate(req *ImageRequest) error
-	// Generate creates a signature for a request
-	Generate(req *ImageRequest) string
-}
-
-// Allowlist checks if a URL is allowlisted (no signature required)
-type Allowlist interface {
-	// IsAllowlisted returns true if the URL doesn't require a signature
-	IsAllowlisted(u *url.URL) bool
-}
-
-// Storage handles persistent storage of cached content
-type Storage interface {
-	// Store saves content and returns its hash
-	Store(ctx context.Context, content io.Reader) (hash string, err error)
-	// Load retrieves content by hash
-	Load(ctx context.Context, hash string) (io.ReadCloser, error)
-	// Delete removes content by hash
-	Delete(ctx context.Context, hash string) error
-	// Exists checks if content exists
-	Exists(ctx context.Context, hash string) (bool, error)
-}
diff --git a/internal/imgcache/service.go b/internal/imgcache/service.go
index 77c7ce9..968dd95 100644
--- a/internal/imgcache/service.go
+++ b/internal/imgcache/service.go
@@ -56,11 +56,10 @@ type ServiceConfig struct {
 	Logger *slog.Logger
 }
 
-// Static errors for service construction and unimplemented operations.
+// Static errors for service construction.
 var (
-	errCacheRequired       = errors.New("cache is required")
-	errSigningKeyRequired  = errors.New("signing key is required")
-	errPurgeNotImplemented = errors.New("purge not implemented")
+	errCacheRequired      = errors.New("cache is required")
+	errSigningKeyRequired = errors.New("signing key is required")
 )
 
 // NewService creates a new image service.
@@ -189,11 +188,6 @@ func (s *Service) Warm(ctx context.Context, req *ImageRequest) error {
 	return err
 }
 
-// Purge removes a cached image. Purging is not implemented yet.
-func (s *Service) Purge(_ context.Context, _ *ImageRequest) error {
-	return errPurgeNotImplemented
-}
-
 // Stats returns cache statistics.
 func (s *Service) Stats(ctx context.Context) (*CacheStats, error) {
 	return s.cache.Stats(ctx)