diff --git a/README.md b/README.md
index d0f2199..a335858 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,31 @@
 # ppsh
-A simple shell screenshot tool, named after the PPSh,
-  a Soviet submachine gun, because it shoots and ends with `sh`.
+A simple shell screenshot tool that uploads to an ssh server,
+  named after the PPSh, a Soviet submachine gun, because it shoots and ends with `sh`.
 
 Replacement for my old python script because finding a maintained SFTP library for Python is more effort than it’s worth.
+
+## Usage
+
+```sh
+ppsh
+```
+
+to capture a screenshot and upload it or
+
+```sh
+ppsh file.png
+```
+
+to upload `file.png` to the remote server.
+
+## Configuration
+
+The first few lines of the script are the config variables.
+Use them to set the remote host, destination folder, etc.
+
+## Dependencies
+
+This script will work on Xorg and Wayland by checking the `WAYLAND_DISPLAY` environment variable.
+
+When used on Xorg, it requires `maim` for the image capture and `xsel` for clipboard management.  
+When used on Wayland, it requires `grim`/`slurp` for the image capture and `wl-copy` for clipboard management.
diff --git a/ppsh b/ppsh
index a02eecd..080f2c3 100755
--- a/ppsh
+++ b/ppsh
@@ -39,18 +39,33 @@ exists() {
 }
 
 main() {
-  filename="$prefix$(generate_name $random_chars).png"
-  date_folder="$(date "+$date_format")"
-  local_directory="$local_root/$date_folder"
-  mkdir -p "$local_directory"
-  capture_and_upload "$local_directory/$filename" "$remote_directory/$filename"
+  if [ -n "$1" ]; then
+    ext="$(echo "$1" | awk '{ n=split($0, a, "."); print a[n] }')"
+    if [ "$ext" == "$1" ]; then # file has no extension
+      filename="$prefix$(generate_name $random_chars)"
+    else 
+      filename="$prefix$(generate_name $random_chars).$ext"
+    fi
+    local_file="$1"
+  else
+    filename="$prefix$(generate_name $random_chars).png"
+    date_folder="$(date "+$date_format")"
+    local_directory="$local_root/$date_folder"
+    mkdir -p "$local_directory"
+    local_file="$local_directory/$filename"
+  fi
+  capture_and_upload "$local_file" "$remote_directory/$filename"
 }
 
 capture_and_upload() {
   local_file="$1"
   remote_file="$2"
   if [ ! "$(exists "$remote_file")" ]; then
-    capture "$local_file"
+    # If the file already exists, we’re in file upload mode.
+    # If it doesn’t, capture a screenshot and save it there.
+    if [ ! -f "$local_file" ]; then
+      capture "$local_file"
+    fi
     upload "$local_file" "$remote_file"
     full_url="$url_template/$filename"
     clipboard "$full_url"
@@ -61,4 +76,4 @@ capture_and_upload() {
   fi
 }
 
-main
+main "$1"