diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 701b424..def5c49 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -10,6 +10,12 @@ on:
     branches:
     - master
 
+env:
+  # Increment to invalidate github actions caches if they become corrupt.
+  # Errors of the form "can't find crate for `snafu_derive` which `snafu` depends on"
+  # can usually be fixed by incrementing this value.
+  CACHE_KEY_PREFIX: 2
+
 jobs:
   all:
     name: All
@@ -45,23 +51,31 @@ jobs:
       with:
         fetch-depth: 0
 
+    # An issue with BSD Tar causes sporadic failures on macOS.
+    # c.f https://github.com/actions/cache/issues/403
+    - name: Install GNU Tar
+      if: matrix.build == 'macos'
+      run: |
+        brew install gnu-tar
+        echo "::add-path::/usr/local/opt/gnu-tar/libexec/gnubin"
+
     - name: Cache cargo registry
       uses: actions/cache@v1
       with:
         path: ~/.cargo/registry
-        key: v1-${{ runner.os }}-cargo-registry
+        key: ${{ env.CACHE_KEY_PREFIX }}-${{ runner.os }}-cargo-registry
 
     - name: Cache cargo index
       uses: actions/cache@v1
       with:
         path: ~/.cargo/git
-        key: v1-${{ runner.os }}-cargo-index
+        key: ${{ env.CACHE_KEY_PREFIX }}-${{ runner.os }}-cargo-index
 
     - name: Cache cargo build
       uses: actions/cache@v1
       with:
         path: target
-        key: v1-${{ runner.os }}-cargo-build-target
+        key: ${{ env.CACHE_KEY_PREFIX }}-${{ runner.os }}-cargo-build-target
 
     - name: Install Stable
       uses: actions-rs/toolchain@v1
diff --git a/Cargo.lock b/Cargo.lock
index 4479f82..c0ef95c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -626,6 +626,7 @@ dependencies = [
  "serde",
  "serde-hex",
  "serde_bytes",
+ "serde_json",
  "serde_with",
  "sha1",
  "snafu",
diff --git a/Cargo.toml b/Cargo.toml
index 1a9a3df..2aa6154 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -34,6 +34,7 @@ pretty_env_logger = "0.4.0"
 regex             = "1.0.0"
 serde-hex         = "0.1.0"
 serde_bytes       = "0.11.0"
+serde_json        = "1.0.57"
 serde_with        = "1.4.0"
 sha1              = "0.6.0"
 snafu             = "0.6.0"
diff --git a/src/error.rs b/src/error.rs
index 8c9cca3..e6c2130 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -136,6 +136,8 @@ pub(crate) enum Error {
   Unstable { feature: &'static str },
   #[snafu(display("Torrent verification failed."))]
   Verify,
+  #[snafu(display("Failed to serialize JSON: {}", source))]
+  JsonSerialize { source: serde_json::Error },
 }
 
 impl Error {
diff --git a/src/subcommand/torrent/show.rs b/src/subcommand/torrent/show.rs
index 346180b..e4216e4 100644
--- a/src/subcommand/torrent/show.rs
+++ b/src/subcommand/torrent/show.rs
@@ -9,6 +9,10 @@ const INPUT_POSITIONAL: &str = "<INPUT>";
 
 const INPUT_VALUE: &str = "INPUT";
 
+const JSON_OUTPUT: &str = "json";
+
+const JSON_HELP: &str = "Output data as JSON instead of the default format.";
+
 #[derive(StructOpt)]
 #[structopt(
   help_message(consts::HELP_MESSAGE),
@@ -36,6 +40,13 @@ pub(crate) struct Show {
     help = INPUT_HELP,
   )]
   input_positional: Option<InputTarget>,
+  #[structopt(
+    name = JSON_OUTPUT,
+    long = "json",
+    short = "j",
+    help = JSON_HELP,
+  )]
+  json: bool,
 }
 
 impl Show {
@@ -49,7 +60,11 @@ impl Show {
 
     let input = env.read(target)?;
     let summary = TorrentSummary::from_input(&input)?;
-    summary.write(env)?;
+    if self.json {
+      summary.write_json(env)?;
+    } else {
+      summary.write(env)?;
+    }
     Ok(())
   }
 }
@@ -559,4 +574,63 @@ files\tNAME
 
     Ok(())
   }
+
+  #[test]
+  fn output_json() {
+    {
+      let metainfo = Metainfo::test_value_single();
+      let mut want = r#"{"name":"NAME","comment":"COMMENT","creation_date":1,
+"created_by":"CREATED BY","source":"SOURCE","info_hash":"5d6f53772b4c20536fcce0c4c364d764a6efa39c",
+"torrent_size":509,"content_size":32768,"private":true,"tracker":
+"udp://announce.example:1337","announce_list":[["http://a.example:4567",
+"https://b.example:77"],["udp://c.example:88"]],"update_url":"https://update.example/",
+"dht_nodes":["node.example:12","1.1.1.1:16","[2001:db8:85a3::8a2e:370]:7334"],
+"piece_size":16384,"piece_count":2,"file_count":1,"files":["NAME"]}"#
+        .replace('\n', "");
+      want.push('\n');
+      let mut env = TestEnvBuilder::new()
+        .arg_slice(&[
+          "imdl",
+          "torrent",
+          "show",
+          "--input",
+          "foo.torrent",
+          "--json",
+        ])
+        .out_is_term()
+        .build();
+      let path = env.resolve("foo.torrent").unwrap();
+      metainfo.dump(path).unwrap();
+      env.assert_ok();
+      let have = env.out();
+      assert_eq!(have, want);
+    }
+
+    {
+      let metainfo = Metainfo::test_value_single_unset();
+      let mut want = r#"{"name":"NAME","comment":null,"creation_date":null,
+"created_by":null,"source":null,"info_hash":"a9105b0ff5f7cefeee5599ed7831749be21cc04e",
+"torrent_size":85,"content_size":5,"private":false,"tracker":null,"announce_list":[],
+"update_url":null,"dht_nodes":[],"piece_size":1024,"piece_count":1,"file_count":1,
+"files":["NAME"]}"#
+        .replace('\n', "");
+      want.push('\n');
+      let mut env = TestEnvBuilder::new()
+        .arg_slice(&[
+          "imdl",
+          "torrent",
+          "show",
+          "--input",
+          "foo.torrent",
+          "--json",
+        ])
+        .out_is_term()
+        .build();
+      let path = env.resolve("foo.torrent").unwrap();
+      metainfo.dump(path).unwrap();
+      env.assert_ok();
+      let have = env.out();
+      assert_eq!(have, want);
+    }
+  }
 }
diff --git a/src/torrent_summary.rs b/src/torrent_summary.rs
index 2081e78..43366f7 100644
--- a/src/torrent_summary.rs
+++ b/src/torrent_summary.rs
@@ -6,6 +6,27 @@ pub(crate) struct TorrentSummary {
   size: Bytes,
 }
 
+#[derive(Serialize)]
+pub(crate) struct TorrentSummaryJson {
+  name: String,
+  comment: Option<String>,
+  creation_date: Option<u64>,
+  created_by: Option<String>,
+  source: Option<String>,
+  info_hash: String,
+  torrent_size: u64,
+  content_size: u64,
+  private: bool,
+  tracker: Option<String>,
+  announce_list: Vec<Vec<String>>,
+  update_url: Option<String>,
+  dht_nodes: Vec<String>,
+  piece_size: u64,
+  piece_count: usize,
+  file_count: usize,
+  files: Vec<String>,
+}
+
 impl TorrentSummary {
   fn new(metainfo: Metainfo, infohash: Infohash, size: Bytes) -> Self {
     Self {
@@ -146,4 +167,70 @@ impl TorrentSummary {
 
     table
   }
+
+  pub(crate) fn write_json(&self, env: &mut Env) -> Result<()> {
+    let data = self.torrent_summary_data();
+    let json = serde_json::to_string(&data).context(error::JsonSerialize)?;
+    outln!(env, "{}", json)?;
+    Ok(())
+  }
+
+  fn torrent_summary_data(&self) -> TorrentSummaryJson {
+    let (file_count, files) = match &self.metainfo.info.mode {
+      Mode::Single { .. } => (1, vec![self.metainfo.info.name.to_string()]),
+      Mode::Multiple { files } => (
+        files.len(),
+        files
+          .iter()
+          .map(|file_info| {
+            format!(
+              "{}",
+              file_info
+                .path
+                .absolute(Path::new(&self.metainfo.info.name))
+                .as_path()
+                .display()
+            )
+          })
+          .collect(),
+      ),
+    };
+
+    TorrentSummaryJson {
+      name: self.metainfo.info.name.to_string(),
+      comment: self.metainfo.comment.clone(),
+      creation_date: self.metainfo.creation_date,
+      created_by: self.metainfo.created_by.clone(),
+      source: self.metainfo.info.source.clone(),
+      info_hash: self.infohash.to_string(),
+      torrent_size: self.size.count(),
+      content_size: self.metainfo.content_size().count(),
+      private: self.metainfo.info.private.unwrap_or_default(),
+      tracker: self.metainfo.announce.clone(),
+      announce_list: self
+        .metainfo
+        .announce_list
+        .as_ref()
+        .map(Clone::clone)
+        .unwrap_or_default(),
+      update_url: self
+        .metainfo
+        .info
+        .update_url
+        .as_ref()
+        .map(ToString::to_string),
+      dht_nodes: self
+        .metainfo
+        .nodes
+        .as_ref()
+        .unwrap_or(&Vec::new())
+        .iter()
+        .map(ToString::to_string)
+        .collect::<Vec<String>>(),
+      piece_size: self.metainfo.info.piece_length.count(),
+      piece_count: self.metainfo.info.pieces.count(),
+      file_count,
+      files,
+    }
+  }
 }