diff --git a/README.md b/README.md
index ceff543..fce28d9 100644
--- a/README.md
+++ b/README.md
@@ -44,6 +44,7 @@ The following flags are supported:
 | `--show-details`                     | show request details in the error page response (if supported by the template)                                                                                                                                                                                                                                            |                  `false`                  |       `SHOW_DETAILS`        |
 | `--proxy-headers="…"`                | HTTP headers listed here will be proxied from the original request to the error page response (comma-separated list)                                                                                                                                                                                                      | `X-Request-Id,X-Trace-Id,X-Amzn-Trace-Id` |    `PROXY_HTTP_HEADERS`     |
 | `--rotation-mode="…"`                | templates automatic rotation mode (disabled/random-on-startup/random-on-each-request/random-hourly/random-daily)                                                                                                                                                                                                          |                `disabled`                 |  `TEMPLATES_ROTATION_MODE`  |
+| `--read-buffer-size="…"`             | per-connection buffer size in bytes for reading requests, this also limits the maximum header size (increase this buffer if your clients send multi-KB Request URIs and/or multi-KB headers (e.g., large cookies), note that increasing this value will increase memory consumption)                                      |                  `5120`                   |     `READ_BUFFER_SIZE`      |
 
 ### `build` command (aliases: `b`)
 
@@ -90,7 +91,7 @@ The following templates are built-in and available for use without any additiona
 
 > [!NOTE]
 > The `cat` template is the only one of those that fetches resources (the actual cat pictures)
-> from external servers - all other templates are self contained.
+> from external servers - all other templates are self-contained.
 
 <table>
   <thead>
diff --git a/internal/cli/serve/command.go b/internal/cli/serve/command.go
index 9d01d60..80acc7c 100644
--- a/internal/cli/serve/command.go
+++ b/internal/cli/serve/command.go
@@ -22,9 +22,9 @@ type command struct {
 
 	opt struct {
 		http struct { // our HTTP server
-			addr string
-			port uint16
-			// readBufferSize uint
+			addr           string
+			port           uint16
+			readBufferSize uint
 		}
 	}
 }
@@ -140,6 +140,15 @@ func NewCommand(log *logger.Logger) *cli.Command { //nolint:funlen,gocognit,gocy
 				return nil
 			},
 		}
+		readBufferSizeFlag = cli.UintFlag{
+			Name: "read-buffer-size",
+			Usage: "per-connection buffer size in bytes for reading requests, this also limits the maximum header size " +
+				"(increase this buffer if your clients send multi-KB Request URIs and/or multi-KB headers (e.g., " +
+				"large cookies), note that increasing this value will increase memory consumption)",
+			Value:    1024 * 5, //nolint:mnd // 5 KB
+			Sources:  env("READ_BUFFER_SIZE"),
+			OnlyOnce: true,
+		}
 	)
 
 	// override some flag usage messages
@@ -157,6 +166,7 @@ func NewCommand(log *logger.Logger) *cli.Command { //nolint:funlen,gocognit,gocy
 		Action: func(ctx context.Context, c *cli.Command) error {
 			cmd.opt.http.addr = c.String(addrFlag.Name)
 			cmd.opt.http.port = uint16(c.Uint(portFlag.Name))
+			cmd.opt.http.readBufferSize = uint(c.Uint(readBufferSizeFlag.Name))
 			cfg.L10n.Disable = c.Bool(disableL10nFlag.Name)
 			cfg.DefaultCodeToRender = uint16(c.Uint(defaultCodeToRenderFlag.Name))
 			cfg.RespondWithSameHTTPCode = c.Bool(sendSameHTTPCodeFlag.Name)
@@ -282,6 +292,7 @@ func NewCommand(log *logger.Logger) *cli.Command { //nolint:funlen,gocognit,gocy
 			&showDetailsFlag,
 			&proxyHeadersListFlag,
 			&rotationModeFlag,
+			&readBufferSizeFlag,
 		},
 	}
 
@@ -290,7 +301,7 @@ func NewCommand(log *logger.Logger) *cli.Command { //nolint:funlen,gocognit,gocy
 
 // Run current command.
 func (cmd *command) Run(ctx context.Context, log *logger.Logger, cfg *config.Config) error { //nolint:funlen
-	var srv = appHttp.NewServer(log)
+	var srv = appHttp.NewServer(log, cmd.opt.http.readBufferSize)
 
 	if err := srv.Register(cfg); err != nil {
 		return err
diff --git a/internal/http/server.go b/internal/http/server.go
index 7b1df00..faf591a 100644
--- a/internal/http/server.go
+++ b/internal/http/server.go
@@ -28,11 +28,10 @@ type Server struct {
 }
 
 // NewServer creates a new HTTP server.
-func NewServer(log *logger.Logger) Server {
+func NewServer(log *logger.Logger, readBufferSize uint) Server {
 	const (
-		readTimeout    = 30 * time.Second
-		writeTimeout   = readTimeout + 10*time.Second // should be bigger than the read timeout
-		maxHeaderBytes = (1 << 20) * 5                //nolint:mnd // 5 MB
+		readTimeout  = 30 * time.Second
+		writeTimeout = readTimeout + 10*time.Second // should be bigger than the read timeout
 	)
 
 	return Server{
@@ -40,7 +39,7 @@ func NewServer(log *logger.Logger) Server {
 		server: &fasthttp.Server{
 			ReadTimeout:                  readTimeout,
 			WriteTimeout:                 writeTimeout,
-			ReadBufferSize:               maxHeaderBytes,
+			ReadBufferSize:               int(readBufferSize),
 			DisablePreParseMultipartForm: true,
 			NoDefaultServerHeader:        true,
 			CloseOnShutdown:              true,
diff --git a/internal/http/server_test.go b/internal/http/server_test.go
index 754c640..96981b9 100644
--- a/internal/http/server_test.go
+++ b/internal/http/server_test.go
@@ -20,7 +20,7 @@ import (
 // TestRouting in fact is a test for the whole server, because it tests all the routes and their handlers.
 func TestRouting(t *testing.T) {
 	var (
-		srv = appHttp.NewServer(logger.NewNop())
+		srv = appHttp.NewServer(logger.NewNop(), 1025*5)
 		cfg = config.New()
 	)