diff --git a/config.inc.sh-example b/config.inc.sh-example
index 87841eb..08d8ec9 100755
--- a/config.inc.sh-example
+++ b/config.inc.sh-example
@@ -4,3 +4,4 @@ BOT_TOKEN=
 ALLOWED_USERIDS=
 ADMIN_USERIDS=
 ALLOWED_GROUPIDS=
+MAX_SIZE=
diff --git a/debug-run.sh b/debug-run.sh
deleted file mode 100755
index 50123ad..0000000
--- a/debug-run.sh
+++ /dev/null
@@ -1,11 +0,0 @@
-#!/bin/bash
-
-. config.inc.sh
-
-API_ID=$API_ID \
-API_HASH=$API_HASH \
-BOT_TOKEN=$BOT_TOKEN \
-ALLOWED_USERIDS=$ALLOWED_USERIDS \
-ADMIN_USERIDS=$ADMIN_USERIDS \
-ALLOWED_GROUPIDS=$ALLOWED_GROUPIDS \
-go run *.go
diff --git a/params.go b/params.go
index c67e8e0..d5d6857 100644
--- a/params.go
+++ b/params.go
@@ -8,6 +8,7 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/dustin/go-humanize"
 	"github.com/wader/goutubedl"
 	"golang.org/x/exp/slices"
 )
@@ -20,6 +21,8 @@ type paramsType struct {
 	AllowedUserIDs  []int64
 	AdminUserIDs    []int64
 	AllowedGroupIDs []int64
+
+	MaxSize int64
 }
 
 var params paramsType
@@ -40,6 +43,8 @@ func (p *paramsType) Init() error {
 	flag.StringVar(&adminUserIDs, "admin-user-ids", "", "admin telegram user ids")
 	var allowedGroupIDs string
 	flag.StringVar(&allowedGroupIDs, "allowed-group-ids", "", "allowed telegram group ids")
+	var maxSize string
+	flag.StringVar(&maxSize, "max-size", "", "allowed max size of video files")
 	flag.Parse()
 
 	var err error
@@ -51,7 +56,7 @@ func (p *paramsType) Init() error {
 	}
 	p.ApiID, err = strconv.Atoi(apiID)
 	if err != nil {
-		return fmt.Errorf("invalid env var API_ID")
+		return fmt.Errorf("invalid api_id")
 	}
 
 	if p.ApiHash == "" {
@@ -89,7 +94,7 @@ func (p *paramsType) Init() error {
 		}
 		id, err := strconv.ParseInt(idStr, 10, 64)
 		if err != nil {
-			return fmt.Errorf("env var ALLOWED_USERIDS contains invalid user ID: " + idStr)
+			return fmt.Errorf("allowed user ids contains invalid user ID: " + idStr)
 		}
 		p.AllowedUserIDs = append(p.AllowedUserIDs, id)
 	}
@@ -104,7 +109,7 @@ func (p *paramsType) Init() error {
 		}
 		id, err := strconv.ParseInt(idStr, 10, 64)
 		if err != nil {
-			return fmt.Errorf("env var ADMIN_USERIDS contains invalid user ID: " + idStr)
+			return fmt.Errorf("admin ids contains invalid user ID: " + idStr)
 		}
 		p.AdminUserIDs = append(p.AdminUserIDs, id)
 		if !slices.Contains(p.AllowedUserIDs, id) {
@@ -122,11 +127,22 @@ func (p *paramsType) Init() error {
 		}
 		id, err := strconv.ParseInt(idStr, 10, 64)
 		if err != nil {
-			return fmt.Errorf("env var ALLOWED_GROUPIDS contains invalid group ID: " + idStr)
+			return fmt.Errorf("allowed group ids contains invalid group ID: " + idStr)
 		}
 		p.AllowedGroupIDs = append(p.AllowedUserIDs, id)
 	}
 
+	if maxSize == "" {
+		maxSize = os.Getenv("MAX_SIZE")
+	}
+	if maxSize != "" {
+		b, err := humanize.ParseBigBytes(maxSize)
+		if err != nil {
+			return fmt.Errorf("invalid max size: %w", err)
+		}
+		p.MaxSize = b.Int64()
+	}
+
 	// Writing env. var YTDLP_COOKIES contents to a file.
 	// In case a docker container is used, the yt-dlp.conf points yt-dlp to this cookie file.
 	if cookies := os.Getenv("YTDLP_COOKIES"); cookies != "" {
diff --git a/run.sh b/run.sh
index 663d9c5..d1b4b00 100755
--- a/run.sh
+++ b/run.sh
@@ -2,10 +2,16 @@
 
 . config.inc.sh
 
+bin=./yt-dlp-telegram-bot
+if [ ! -x "$bin" ]; then
+	bin="go run *.go"
+fi
+
 API_ID=$API_ID \
 API_HASH=$API_HASH \
 BOT_TOKEN=$BOT_TOKEN \
 ALLOWED_USERIDS=$ALLOWED_USERIDS \
 ADMIN_USERIDS=$ADMIN_USERIDS \
 ALLOWED_GROUPIDS=$ALLOWED_GROUPIDS \
-./yt-dlp-telegram-bot
+MAX_SIZE=$MAX_SIZE \
+$bin
diff --git a/upload.go b/upload.go
index 9b028d4..daabf55 100644
--- a/upload.go
+++ b/upload.go
@@ -34,6 +34,9 @@ func (p *Uploader) UploadFile(ctx context.Context, entities tg.Entities, u *tg.U
 		if n == 0 {
 			break
 		}
+		if params.MaxSize > 0 && buf.Len() > int(params.MaxSize) {
+			return fmt.Errorf("file is too big, max. allowed size is %s", humanize.BigBytes(big.NewInt(int64(params.MaxSize))))
+		}
 		buf.Write(b[:n])
 	}