diff --git a/internal/backend/characters.go b/internal/backend/characters.go
index c23f26a..0a8cd73 100644
--- a/internal/backend/characters.go
+++ b/internal/backend/characters.go
@@ -37,6 +37,33 @@ func (c *CharacterService) List() ([]string, error) {
 	return characters, nil
 }
 
+// CharacterDetails is a character image with the time its file was last changed, so a
+// client that caches images knows when to download one again.
+type CharacterDetails struct {
+	Name     string `json:"name" doc:"File name of the character image"`
+	Modified int64  `json:"modified" doc:"When the image was last changed, in Unix seconds"`
+}
+
+// ListDetails returns all character images with the time each was last changed.
+func (c *CharacterService) ListDetails() ([]CharacterDetails, error) {
+	entries, err := fs.ReadDir(c.root.FS(), ".")
+	if err != nil {
+		return nil, err
+	}
+	characters := []CharacterDetails{}
+	for _, entry := range entries {
+		if entry.IsDir() || !isImage(entry.Name()) {
+			continue
+		}
+		info, err := entry.Info()
+		if err != nil {
+			return nil, err
+		}
+		characters = append(characters, CharacterDetails{Name: entry.Name(), Modified: info.ModTime().Unix()})
+	}
+	return characters, nil
+}
+
 // Open opens the character image with the given file name.
 func (c *CharacterService) Open(name string) (*os.File, error) {
 	if name == "" || name != filepath.Base(name) || !isImage(name) {
diff --git a/internal/backend/characters_test.go b/internal/backend/characters_test.go
index e25a076..ec73209 100644
--- a/internal/backend/characters_test.go
+++ b/internal/backend/characters_test.go
@@ -4,6 +4,7 @@ import (
 	"io"
 	"path/filepath"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -31,6 +32,32 @@ func TestCharacterList(t *testing.T) {
 	assert.Equal(t, []string{"Adol.png", "Aloy.JPG"}, characters)
 }
 
+func TestCharacterListDetails(t *testing.T) {
+	c := newCharacterService(t)
+	changed := time.Date(2026, 10, 7, 12, 0, 0, 0, time.UTC)
+	require.NoError(t, c.root.Chtimes("Adol.png", changed, changed))
+
+	characters, err := c.ListDetails()
+	require.NoError(t, err)
+	require.Len(t, characters, 2)
+	assert.Equal(t, CharacterDetails{Name: "Adol.png", Modified: changed.Unix()}, characters[0])
+	assert.Equal(t, "Aloy.JPG", characters[1].Name)
+}
+
+func TestCharacterListDetailsSeesChangedImage(t *testing.T) {
+	c := newCharacterService(t)
+	before, err := c.ListDetails()
+	require.NoError(t, err)
+
+	later := time.Unix(before[0].Modified, 0).Add(time.Hour)
+	require.NoError(t, c.root.Chtimes("Adol.png", later, later))
+
+	after, err := c.ListDetails()
+	require.NoError(t, err)
+	assert.Greater(t, after[0].Modified, before[0].Modified)
+	assert.Equal(t, before[1], after[1], "unchanged images keep their time")
+}
+
 func TestCharacterOpen(t *testing.T) {
 	c := newCharacterService(t)
 
diff --git a/internal/server/handlers_test.go b/internal/server/handlers_test.go
index e613851..e5f8488 100644
--- a/internal/server/handlers_test.go
+++ b/internal/server/handlers_test.go
@@ -167,6 +167,16 @@ func TestCharacterEndpoints(t *testing.T) {
 	require.NoError(t, json.Unmarshal(e.do(http.MethodGet, "/api/v1/character/list").Body.Bytes(), &list))
 	assert.Equal(t, []string{"Adol.png", "Aloy.jpg"}, list)
 
+	var details []struct {
+		Name     string `json:"name"`
+		Modified int64  `json:"modified"`
+	}
+	require.NoError(t, json.Unmarshal(e.do(http.MethodGet, "/api/v1/character/details").Body.Bytes(), &details))
+	require.Len(t, details, 2)
+	assert.Equal(t, "Adol.png", details[0].Name)
+	assert.Equal(t, "Aloy.jpg", details[1].Name)
+	assert.Positive(t, details[0].Modified)
+
 	rec := e.do(http.MethodGet, "/api/v1/character?name=Adol.png")
 	assert.Equal(t, http.StatusOK, rec.Code)
 	assert.Equal(t, "image/png", rec.Header().Get("Content-Type"))
diff --git a/internal/server/misc_handler.go b/internal/server/misc_handler.go
index ba92152..59f9a42 100644
--- a/internal/server/misc_handler.go
+++ b/internal/server/misc_handler.go
@@ -57,6 +57,12 @@ func (s *Server) registerMisc(a huma.API) {
 		func(ctx context.Context, _ *struct{}) (*jsonBody[[]string], error) {
 			return ok(s.characters.List())
 		})
+	register(s, a, route{op: get("list-character-details", "/character/details", "characters",
+		"List characters with change times",
+		"Returns every character image with the time it was last changed, so clients can cache images and download only the changed ones.")},
+		func(ctx context.Context, _ *struct{}) (*jsonBody[[]backend.CharacterDetails], error) {
+			return ok(s.characters.ListDetails())
+		})
 	image := get("get-character", "/character", "characters", "Character image",
 		"Returns a character image.", http.StatusBadRequest, http.StatusNotFound)
 	image.Responses = fileResponses("The image", "image/png", "image/jpeg")
diff --git a/internal/server/openapi_test.go b/internal/server/openapi_test.go
index 495e543..d37b7ba 100644
--- a/internal/server/openapi_test.go
+++ b/internal/server/openapi_test.go
@@ -76,6 +76,7 @@ func TestOpenAPIDocumentsTheV1API(t *testing.T) {
 	assert.Equal(t, []string{
 		"DELETE /api/v1/token",
 		"GET /api/v1/character",
+		"GET /api/v1/character/details",
 		"GET /api/v1/character/list",
 		"GET /api/v1/download",
 		"GET /api/v1/download/linux",
@@ -207,6 +208,7 @@ func TestResponsesMatchOpenAPI(t *testing.T) {
 
 	// Characters, downloads, server info.
 	v.check(http.MethodGet, "/api/v1/character/list", "", http.StatusOK)
+	v.check(http.MethodGet, "/api/v1/character/details", "", http.StatusOK)
 	v.check(http.MethodGet, "/api/v1/character?name=Aloy.jpg", "", http.StatusOK)
 	v.check(http.MethodGet, "/api/v1/character?name=../secret.png", "", http.StatusBadRequest)
 	v.check(http.MethodGet, "/api/v1/character?name=Missing.png", "", http.StatusNotFound)