diff --git a/README.md b/README.md
index 7f152cb..ec5fd02 100644
--- a/README.md
+++ b/README.md
@@ -2,10 +2,28 @@
 
 ## Setup
 
-You need to compile the FUSE filesystem (written in C), then install
-the browser extension which runs it and talks to it.
+First, install the browser extension.
 
-### Run the C filesystem
+Then, install the C filesystem.
+
+### Install the browser extension
+
+(I think it will work on Edge or Opera or whatever, too. You'll need to
+change the native messaging path in install.sh in those cases.)
+
+#### Chrome
+
+Go to the [Chrome extensions page](chrome://extensions). Enable
+Developer mode (top-right corner).
+
+Load-unpacked the `extension/` folder in this repo.
+
+Get the extension ID.
+
+#### Firefox
+
+
+### Install the C filesystem
 
 First, make sure you `git submodule update --init` to get the
 `fs/cJSON` and `fs/base64` dependencies.
@@ -26,21 +44,43 @@ extension can launch and talk to the filesystem:
 $ ./install.sh [chrome | chromium | firefox]
 ```
 
-### Install the browser extension
+### Ready
 
-I think it will work on Edge or Opera or whatever, too. You'll need to
-change the native messaging path in install.sh
-
-#### Firefox
-
-#### Chrome
-
-Go to the [Chrome extensions page](chrome://extensions).
-
-Enable Developer mode. Load-unpacked the `extension/` folder in this repo.
+Reload the extension in `chrome://extensions`.
 
 Now your browser tabs should be mounted in `fs/mnt`!
 
+## Examples of stuff you can do
+
+(assuming your shell is in the `fs` subdirectory)
+
+### List the titles of all the tabs you have open 
+
+```
+$ cat mnt/tabs/by-id/*/title
+GitHub
+Extensions
+TabFS/install.sh at master · osnr/TabFS
+Alternative Extension Distribution Options - Google Chrome
+Web Store Hosting and Updating - Google Chrome
+Home / Twitter
+...
+```
+
+### Close all Stack Overflow tabs
+
+```
+$ echo close | tee -a mnt/tabs/by-title/*Stack_Overflow*/control
+```
+
+### Save text of all tabs to a file
+
+(wip, FIXME)
+
+```
+$ cat mnt/tabs/by-id/*/text > text.txt
+```
+
 ## Design
 
 - `extension/`: Browser extension, written in JS
diff --git a/install.sh b/install.sh
index aa13668..04d96e4 100755
--- a/install.sh
+++ b/install.sh
@@ -1,7 +1,14 @@
 #!/bin/bash -eux
 
+if [[ ! ( ( "$1" == "firefox" && "$#" -eq 1 ) ||
+              ( "$1" == "chrome" && "$#" -eq 2 && ${#2} -eq 32) ||
+              ( "$1" == "chromium" && "$#" -eq 2 && ${#2} -eq 32) ) ]]; then
+    echo "Usage: $0 <chrome EXTENSION_ID | chromium EXTENSION_ID | firefox>"
+    exit 2
+fi
+    
 OS="$(uname -s)"
-BROWSER="$(echo ${1:-chrome} | tr '[:upper:]' '[:lower:]')"
+BROWSER="$(echo $1 | tr '[:upper:]' '[:lower:]')"
 
 # https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_manifests#Manifest_location
 # https://developer.chrome.com/extensions/nativeMessaging#native-messaging-host-location
@@ -27,6 +34,7 @@ EXE_PATH=$(pwd)/fs/tabfs
 
 case "$BROWSER" in
     chrome | chromium)
+        EXTENSION_ID=$2
         MANIFEST=$(cat <<EOF
 {
   "name": "$APP_NAME",
@@ -34,7 +42,7 @@ case "$BROWSER" in
   "path": "$EXE_PATH",
   "type": "stdio",
   "allowed_extensions": ["tabfs@rsnous.com"],
-  "allowed_origins": ["chrome-extension://jimpolemfaeckpjijgapgkmolankohgj/"]
+  "allowed_origins": ["chrome-extension://$EXTENSION_ID/"]
 }
 EOF
         );;