diff --git a/Cargo.lock b/Cargo.lock
index 7fd809b..cd65f09 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1585,7 +1585,7 @@ dependencies = [
 
 [[package]]
 name = "transbeam"
-version = "0.1.0"
+version = "0.2.0"
 dependencies = [
  "actix",
  "actix-files",
diff --git a/Cargo.toml b/Cargo.toml
index 5c71047..9cd2f20 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "transbeam"
-version = "0.1.0"
+version = "0.2.0"
 authors = ["xenofem <xenofem@xeno.science>"]
 edition = "2021"
 license = "MIT"
diff --git a/README.md b/README.md
index 3015747..00e4ab4 100644
--- a/README.md
+++ b/README.md
@@ -28,6 +28,8 @@ transbeam is configured with the following environment variables:
   (default: `./storage`)
 - `TRANSBEAM_STATIC_DIR`: path where the web app's static files live
   (default: `./static`)
+- `TRANSBEAM_BASE_URL`: base URL for this transbeam instance, without
+  trailing `/`
 - `TRANSBEAM_PORT`: port to listen on localhost for http requests
   (default: 8080)
 - `TRANSBEAM_REVERSE_PROXY`: whether transbeam is running behind a
diff --git a/src/main.rs b/src/main.rs
index cf591ab..77f49ae 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -30,6 +30,7 @@ struct AppState {
 }
 
 struct Config {
+    base_url: String,
     max_upload_size: u64,
     max_lifetime: u16,
     upload_password: String,
@@ -58,12 +59,14 @@ pub fn log_auth_failure(ip_addr: &str) {
 #[template(path = "index.html")]
 struct IndexPage {
     cachebuster: String,
+    base_url: String,
 }
 
 #[get("/")]
 async fn index(data: web::Data<AppState>) -> impl Responder {
     IndexPage {
         cachebuster: data.config.cachebuster.clone(),
+        base_url: data.config.base_url.clone(),
     }
 }
 
@@ -78,6 +81,7 @@ struct DownloadRequest {
 struct DownloadPage<'a> {
     info: DownloadInfo,
     cachebuster: &'a str,
+    base_url: &'a str,
 }
 
 #[derive(Serialize)]
@@ -134,6 +138,7 @@ async fn handle_download(
                 offsets,
             },
             cachebuster: &data.config.cachebuster,
+            base_url: &data.config.base_url,
         }
         .to_response())
     }
@@ -175,6 +180,7 @@ async fn download_info(
 #[template(path = "404.html")]
 struct NotFoundPage<'a> {
     cachebuster: &'a str,
+    base_url: &'a str,
 }
 
 fn not_found<T>(req: HttpRequest, data: web::Data<AppState>, report: bool) -> actix_web::Result<T> {
@@ -184,6 +190,7 @@ fn not_found<T>(req: HttpRequest, data: web::Data<AppState>, report: bool) -> ac
     }
     let mut resp = NotFoundPage {
         cachebuster: &data.config.cachebuster,
+        base_url: &data.config.base_url,
     }
     .to_response();
     *resp.status_mut() = StatusCode::NOT_FOUND;
@@ -269,6 +276,14 @@ where
         .unwrap_or_else(default)
 }
 
+fn env_or_panic<T: FromStr>(var: &str) -> T
+where
+    <T as FromStr>::Err: Debug,
+{
+    let val = std::env::var(var).unwrap_or_else(|_| panic!("{} must be set!", var));
+    val.parse::<T>().unwrap_or_else(|_| panic!("Invalid value {} for variable {}", val, var))
+}
+
 #[actix_web::main]
 async fn main() -> std::io::Result<()> {
     dotenv::dotenv().ok();
@@ -276,6 +291,7 @@ async fn main() -> std::io::Result<()> {
 
     let static_dir: PathBuf = env_or_else("TRANSBEAM_STATIC_DIR", || PathBuf::from("static"));
     let storage_dir: PathBuf = env_or_else("TRANSBEAM_STORAGE_DIR", || PathBuf::from("storage"));
+    let base_url: String = env_or_panic("TRANSBEAM_BASE_URL");
     let port: u16 = env_or("TRANSBEAM_PORT", 8080);
     let mnemonic_codes: bool = env_or("TRANSBEAM_MNEMONIC_CODES", true);
     let reverse_proxy: bool = env_or("TRANSBEAM_REVERSE_PROXY", true);
@@ -284,13 +300,13 @@ async fn main() -> std::io::Result<()> {
         env_or::<ByteSize>("TRANSBEAM_MAX_UPLOAD_SIZE", ByteSize(16 * bytesize::GB)).as_u64();
     let max_storage_size: u64 =
         env_or::<ByteSize>("TRANSBEAM_MAX_STORAGE_SIZE", ByteSize(64 * bytesize::GB)).as_u64();
-    let upload_password: String =
-        std::env::var("TRANSBEAM_UPLOAD_PASSWORD").expect("TRANSBEAM_UPLOAD_PASSWORD must be set!");
+    let upload_password: String = env_or_panic("TRANSBEAM_UPLOAD_PASSWORD");
     let cachebuster: String = env_or_else("TRANSBEAM_CACHEBUSTER", String::new);
 
     let data = web::Data::new(AppState {
         file_store: RwLock::new(FileStore::load(storage_dir.clone(), max_storage_size).await?),
         config: Config {
+            base_url,
             max_upload_size,
             max_lifetime,
             upload_password,
diff --git a/templates/404.html b/templates/404.html
index 55979fa..aed17a9 100644
--- a/templates/404.html
+++ b/templates/404.html
@@ -1,6 +1,8 @@
 {% extends "base.html" %}
 
 {% block title %}Download not found - transbeam{% endblock %}
+{% block og_title %}Download not found{% endblock %}
+{% block og_description %}{% endblock %}
 
 {% block head %}
   <script src="js/download-landing.js?{{ cachebuster }}"></script>
diff --git a/templates/base.html b/templates/base.html
index 0bc7050..6c85945 100644
--- a/templates/base.html
+++ b/templates/base.html
@@ -3,12 +3,18 @@
   <head>
     <meta charset="utf-8"/>
     <meta name="viewport" content="width=device-width, initial-scale=1"/>
-    <meta name="color-scheme" content="light dark">
+    <meta name="color-scheme" content="light dark"/>
     <link rel="stylesheet" type="text/css" href="css/transbeam.css?{{ cachebuster }}"/>
     <link rel="stylesheet" type="text/css" href="css/colors.css?{{ cachebuster }}"/>
     <link rel="apple-touch-icon" href="images/site-icons/transbeam-apple.png"/>
     <link rel="manifest" href="manifest.json"/>
     <title>{% block title %}transbeam{% endblock %}</title>
+    <meta name="og:type" content="website"/>
+    <meta name="og:site_name" content="transbeam"/>
+    <meta name="og:title" content="{% block og_title %}transbeam{% endblock %}"/>
+    <meta name="og:description" content="{% block og_description %}Low-latency file-drop web app{% endblock %}"/>
+    <meta name="og:image" content="{{ base_url }}/images/site-icons/transbeam-192.png"/>
+    <meta name="og:url" content="{{ base_url }}/{% block relative_path %}{% endblock %}"/>
     {% block head %}{% endblock %}
   </head>
   <body {% block body_attrs %}{% endblock %}>
diff --git a/templates/download.html b/templates/download.html
index 4d1c6a6..bd2f7f0 100644
--- a/templates/download.html
+++ b/templates/download.html
@@ -2,6 +2,19 @@
 
 {% block title %}{{ info.file.name }} - transbeam{% endblock %}
 
+{% block og_title %}{{ info.file.name }}{% endblock %}
+{% block og_description -%}
+  {% let formatted_total_size = bytesize::to_string(info.file.size.clone(), false).replace(" ", "") -%}
+  {% match info.file.contents -%}
+    {% when Some with (files) -%}
+      {{ files.len() }} files, {{ formatted_total_size }} total
+    {%- else -%}
+      {{ formatted_total_size }}
+    {%- endmatch %}, expires {{ info.file.expiry.format(DATE_DISPLAY_FORMAT).unwrap() }}
+{%- endblock %}
+
+{% block relative_path %}download?code={{ info.code }}{% endblock %}
+
 {% block head %}
   <script src="js/util.js?{{ cachebuster }}"></script>
   <script type="text/javascript">