diff --git a/Makefile b/Makefile
index 3546650..89c4792 100644
--- a/Makefile
+++ b/Makefile
@@ -27,4 +27,7 @@ firefox:
 clean:
 	@rm -f open-in-mpv Firefox.zip Chrome.crx
 
-.PHONY: all release debug install uninstall firefox clean
\ No newline at end of file
+fmt:
+	clang-format -i src/*.{hpp,cpp}
+
+.PHONY: all release debug install uninstall firefox clean fmt
\ No newline at end of file
diff --git a/README.md b/README.md
index 5384e99..c6a34ed 100644
--- a/README.md
+++ b/README.md
@@ -1,8 +1,14 @@
-# open-in-mpv
+<h1 align="center">open-in-mpv</h1>
+
 This is a simple web extension (for Chrome and Firefox) which helps open any video in the currently open tab in the [mpv player](https://mpv.io).
 
 The extension itself shares a lot of code with the one from the awesome [iina](https://github.com/iina/iina), while the (bare) backend is written in C++20 (this is a rewrite from Rust).
 
+- [Installation](#installation)
+  - [The `mpv://` protocol](#the-mpv-protocol)
+  - [Playlist and `enqueue` functionality](#playlist-and-enqueue-functionality)
+  - [Player support](#player-support)
+
 ## Installation
 > Compiled binaries and packed extensions can be found in the [releases page](https://github.com/Baldomo/open-in-mpv/releases).
 
@@ -15,7 +21,13 @@ sudo make install
 ### The `mpv://` protocol
 `open-in-mpv install-protocol` will create a custom `xdg-open` desktop file with a scheme handler for the `mpv://` protocol. This lets `xdg-open` call `open-in-mpv` with an encoded URI, so that it can be parsed and the information can be relayed to `mpv` - this logic follows how `iina` parses and opens custom URIs with the `iina://` protocol on Mac. `install-protocol.sh` has the same functionality.
 
-The table below is a simple documentation of the URL query keys and values used to let the `open-in-mpv` executable what to do:
+Please note that this specification is enforced quite strictly, as the program will error out when:
+
+- The protocol is not `mpv://`
+- The method/path is not `/open`
+- The query is empty
+
+The table below is a simple documentation of the URL query keys and values used to let the `open-in-mpv` executable what to do.
 
 | Key           | Example value                          | Description |
 |---------------|----------------------------------------|---------------|
@@ -24,7 +36,7 @@ The table below is a simple documentation of the URL query keys and values used
 | `pip`         | `1`                                    | Simulates a picture-in-picture mode (only works with mpv for now) |
 | `enqueue`     | `1`                                    | Adds a video to the queue (see below) |
 | `new_window`  | `1`                                    | Forcibly starts a video in a new window even if one is already open |
-| `player`      | `celluloid`                            | Starts any arbitrary video player (only mpv-based ones are recommended, such as [Celluloid](https://celluloid-player.github.io/)) |
+| `player`      | `celluloid`                            | Starts any supported video player (see [Player support](#player-support)) |
 | `flags`       | `--vo%3Dgpu`                           | Custom command options and flags to be passed to the video player, URL-encoded |
 
 ### Playlist and `enqueue` functionality
@@ -32,4 +44,7 @@ For `enqueue` to work properly with any mpv-based player (provided it supports m
 
 ```conf
 input-ipc-server=/tmp/mpvsocket
-```
\ No newline at end of file
+```
+
+### Player support
+Supported players are defined in `src/players.hpp`, where the struct `player` defines supported functionality and command line flag overrides. To request support for a player you're welcome to open a new issue or a pull request.
\ No newline at end of file
diff --git a/src/main.cpp b/src/main.cpp
index ecfe8be..955796c 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -61,7 +61,7 @@ int main(int argc, char const *argv[]) {
             return 0;
         }
 
-        std::cout << "Error writing to socket, opening new instance"
+        std::cerr << "Error writing to socket, opening new instance"
                   << std::endl;
     }
     std::system(mo->build_cmd().c_str());
diff --git a/src/options.hpp b/src/options.hpp
index 7c6e506..d71093a 100644
--- a/src/options.hpp
+++ b/src/options.hpp
@@ -3,12 +3,35 @@
 #include "players.hpp"
 #include "url.hpp"
 
+#include <algorithm>
+#include <cstdio>
 #include <cstring>
 #include <sstream>
 #include <string>
+#include <vector>
 
 using std::string;
 
+namespace {
+// Replace all occurrences of `from` with `to` in `str`
+string replace_all(string str, const string &from, const string &to) {
+    size_t start_pos = 0;
+    while ((start_pos = str.find(from, start_pos)) != string::npos) {
+        str.replace(start_pos, from.length(), to);
+        // Handles case where 'to' is a substring of 'from'
+        start_pos += to.length();
+    }
+    return str;
+}
+
+// Remove all characters equals to `c` at the beginning of the string
+string lstrip(string str, char c) {
+    while (str.at(0) == c)
+        str.replace(0, 1, "");
+    return str;
+}
+} // namespace
+
 namespace oim {
 
 /*
@@ -27,6 +50,11 @@ class options {
     bool enqueue_;
     bool new_window_;
 
+    /*
+     * Parses flag overrides and returns the final flags
+     */
+    string override_flags();
+
   public:
     /*
      * Constructor for oim::options
@@ -73,12 +101,16 @@ string options::build_cmd() {
     }
 
     ret << player_info_->executable << " ";
-    if (fullscreen_)
+    if (fullscreen_ && !player_info_->fullscreen.empty())
         ret << player_info_->fullscreen << " ";
-    if (pip_)
+    if (pip_ && !player_info_->pip.empty())
         ret << player_info_->pip << " ";
-    if (!flags_.empty())
-        ret << flags_ << " ";
+    if (!flags_.empty()) {
+        if (!player_info_->flag_overrides.empty())
+            ret << override_flags() << " ";
+        else
+            ret << flags_ << " ";
+    }
     ret << url_;
 
     return ret.str();
@@ -99,6 +131,41 @@ string options::build_ipc() {
     return ret.str();
 }
 
+string options::override_flags() {
+    // Return immediatly in case there are no overrides
+    if (player_info_->flag_overrides.empty())
+        return flags_;
+
+    bool star = false;
+    std::ostringstream ret;
+
+    // Check whether there's a global override
+    auto star_pair = player_info_->flag_overrides.find("*");
+    if (star_pair != player_info_->flag_overrides.end())
+        star = true;
+
+    // Turn flags_ into a stream to tokenize somewhat idiomatically
+    auto flagstream = std::istringstream{ flags_ };
+    string tmp;
+
+    while (flagstream >> tmp) {
+        if (star) {
+            // Remove all dashes at the beginning of the flag
+            string stripped = ::lstrip(tmp, '-');
+            ret << ::replace_all((*star_pair).second, "%s", stripped);
+        } else {
+            // Search for the flag currently being processed
+            auto fo = player_info_->flag_overrides.find(tmp);
+            if (fo == player_info_->flag_overrides.end())
+                continue;
+
+            ret << ::replace_all((*fo).second, "%s", tmp);
+        }
+    }
+
+    return ret.str();
+}
+
 void options::parse(const char *url_s) {
     oim::url u(url_s);
 
@@ -119,15 +186,12 @@ void options::parse(const char *url_s) {
     if (player_info_ == nullptr)
         throw string("Unsupported player: ") + player_;
 
-    fullscreen_ = u.query_value("fullscreen") == "1";
+    fullscreen_ = u.query_value("full_screen") == "1";
     pip_ = u.query_value("pip") == "1";
     enqueue_ = u.query_value("enqueue") == "1";
     new_window_ = u.query_value("new_window") == "1";
 }
 
-bool options::needs_ipc() {
-    // For now this is needed only when queuing videos
-    return enqueue_;
-}
+bool options::needs_ipc() { return player_info_->needs_ipc; }
 
 } // namespace oim
\ No newline at end of file
diff --git a/src/players.hpp b/src/players.hpp
index dc37bd5..24409f7 100644
--- a/src/players.hpp
+++ b/src/players.hpp
@@ -27,17 +27,20 @@ struct player {
     bool needs_ipc;
 
     /*
+     * Overrides for any extra command line flag
+     *
      * Override syntax:
      * `"*"`:    matches anything and will take precedence over any other
-     * override e.g. the pair `{"*", ""}` will void all flags
+     *           override
+     *           e.g. the pair `{"*", ""}` will void all flags
      * `"flag"`: matches the flag `--flag`
-     *           e.g. the pair `{"foo", "bar"}` will replace `--foo` with
-     * `--bar`
+     *           e.g. the pair `{"--foo", "--bar"}` will replace `--foo` with
+     *           `--bar`
      * `"%s"`:   is replaced with the original flag without the leading `--`
-     *           e.g. the pair `{"foo", "--%s-bar"}` will replace `--foo` with
-     * `--foo-bar`
+     *           e.g. the pair `{"--foo", "--%s-bar"}` will replace `--foo` with
+     *           `--foo-bar`
      *
-     * Note: command line options with parameters such as --foo=bar are
+     * Note: command line options with parameters such as `--foo=bar` are
      * considered a flags as a whole
      */
     unordered_map<string, string> flag_overrides;
@@ -61,7 +64,7 @@ unordered_map<string, player> player_info = {
         .enqueue = "--enqueue",
         .new_window = "--new-window",
         .needs_ipc = false,
-        .flag_overrides = { { "*", "--mpv-options=%s" } } } }
+        .flag_overrides = { { "*", "--mpv-options=%s" } } } },
 };
 
 player *get_player_info(string name) {