diff --git a/.gitignore b/.gitignore
index 6bb6a68..267a6f9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,4 @@
 /spec/reports/
 /tmp/
 /vendor/bundle
+/vendor/speedscope
diff --git a/Gemfile b/Gemfile
index ec1b8a4..97879fc 100644
--- a/Gemfile
+++ b/Gemfile
@@ -7,5 +7,7 @@ gemspec
 
 gem "activejob"
 gem "rake", "~> 13.0"
+gem "rspec"
+gem "rubyzip"
 gem "sidekiq"
 gem "standard"
diff --git a/Gemfile.lock b/Gemfile.lock
index da0cabd..02921fd 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -91,6 +91,7 @@ GEM
       logger (>= 1.7.0)
       rack (>= 3.2.0)
       redis-client (>= 0.26.0)
+    rubyzip (3.2.2)
     stackprof (0.2.28)
     standard (1.35.1)
       language_server-protocol (~> 3.17.0.2)
@@ -116,6 +117,7 @@ DEPENDENCIES
   activejob
   rake (~> 13.0)
   rspec
+  rubyzip
   sidekiq
   singed!
   standard
diff --git a/Rakefile b/Rakefile
index cd510a0..638ee1b 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,4 +1,55 @@
 # frozen_string_literal: true
 
 require "bundler/gem_tasks"
+require "open-uri"
+require "fileutils"
+require "tmpdir"
+require "zip"
+require_relative "lib/singed/speedscope"
+
+namespace :speedscope do
+  destination_dir = File.expand_path("vendor/speedscope", __dir__)
+
+  desc "Download and unpack speedscope into vendor/speedscope"
+  task vendor: destination_dir
+
+  directory destination_dir do
+    version = Singed::Speedscope::VERSION
+    url = "https://github.com/jlfwong/speedscope/releases/download/v#{version}/speedscope-#{version}.zip"
+
+    unzip_dir = File.expand_path("..", destination_dir) # speedscope dir is in the archive
+    FileUtils.mkdir_p(destination_dir)
+
+    tmp_zip = File.join(Dir.tmpdir, "speedscope-#{version}.zip")
+
+    puts "Downloading speedscope from #{url}"
+    URI.parse(url).open do |remote|
+      File.open(tmp_zip, "wb") do |file|
+        IO.copy_stream(remote, file)
+      end
+    end
+
+    puts "Vendoring speedscope into #{unzip_dir}"
+    Zip::File.open(tmp_zip) do |zip_file|
+      zip_file.each do |entry|
+        destination = File.join(unzip_dir, entry.name)
+        if entry.directory?
+          FileUtils.mkdir_p(destination)
+        else
+          FileUtils.mkdir_p(File.dirname(destination))
+          entry.extract(destination_directory: unzip_dir)
+        end
+      end
+    end
+  end
+
+  desc "Remove the unpacked speedscope directory"
+  task :clobber do
+    FileUtils.rm_rf(destination_dir)
+  end
+end
+
+Rake::Task[:build].enhance ["speedscope:vendor"]
+Rake::Task[:clobber].enhance ["speedscope:clobber"]
+
 task default: %i[]
diff --git a/lib/singed.rb b/lib/singed.rb
index a6bb712..2ac5ba9 100644
--- a/lib/singed.rb
+++ b/lib/singed.rb
@@ -71,6 +71,7 @@ def profiling?
   autoload :Flamegraph, "singed/flamegraph"
   autoload :Report, "singed/report"
   autoload :RackMiddleware, "singed/rack_middleware"
+  autoload :Speedscope, "singed/speedscope"
 end
 
 require "singed/kernel_ext"
diff --git a/lib/singed/flamegraph.rb b/lib/singed/flamegraph.rb
index dec8f6e..d5d78ec 100644
--- a/lib/singed/flamegraph.rb
+++ b/lib/singed/flamegraph.rb
@@ -62,11 +62,11 @@ def save
     end
 
     def open
-      system open_command
+      Singed::Speedscope.open(@filename)
     end
 
     def open_command
-      @open_command ||= "npx speedscope #{@filename}"
+      Singed::Speedscope.open_command(@filename)
     end
 
     def self.generate_filename(label: nil, time: Time.now) # rubocop:disable Rails/TimeZone
diff --git a/lib/singed/kernel_ext.rb b/lib/singed/kernel_ext.rb
index 16cb266..c566b92 100644
--- a/lib/singed/kernel_ext.rb
+++ b/lib/singed/kernel_ext.rb
@@ -8,7 +8,6 @@ def flamegraph(label = nil, open: true, ignore_gc: false, interval: 1000, io: $s
     bright_red = "\e[91m"
     none = "\e[0m"
     if open
-      # use npx, so we don't have to add it as a dependency
       io.puts "🔥📈 #{bright_red}Captured flamegraph, opening with#{none}: #{fg.open_command}"
       fg.open
     else
diff --git a/lib/singed/speedscope.rb b/lib/singed/speedscope.rb
new file mode 100644
index 0000000..d168d9b
--- /dev/null
+++ b/lib/singed/speedscope.rb
@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+require "rbconfig"
+require "tmpdir"
+
+module Singed
+  module Speedscope
+    # Take latest version from https://github.com/jlfwong/speedscope/releases
+    # that have ZIP archive with self-contained version published
+    VERSION = "1.24.0"
+
+    class << self
+      def bundled_index_html
+        File.join(File.expand_path("../..", __dir__), "vendor", "speedscope", "index.html")
+      end
+
+      def open_command(profile_path)
+        if File.exist?(bundled_index_html)
+          "#{os_open_command} file://#{bundled_index_html}#localProfilePath=#{profile_path}"
+        else
+          "npx speedscope #{profile_path}"
+        end
+      end
+
+      def open(profile_path)
+        profile_path = profile_path.to_s
+
+        if File.exist?(bundled_index_html)
+          open_with_bundled_speedscope(profile_path)
+        else
+          open_with_npx(profile_path)
+        end
+      end
+
+      private
+
+      def open_with_npx(profile_path)
+        system("npx", "speedscope", profile_path)
+      end
+
+      # Based on speedscope CLI code (MIT license)
+      # See https://github.com/jlfwong/speedscope/blob/3613918de0dd55a263d0d04f85b0c8c2039c7bee/bin/cli.mjs
+      def open_with_bundled_speedscope(profile_path)
+        source_buffer = File.binread(profile_path)
+        filename = File.basename(profile_path)
+
+        source_base64 = [source_buffer].pack("m0")
+        js_source = "speedscope.loadFileFromBase64(#{filename.inspect}, #{source_base64.inspect})"
+
+        file_prefix = "speedscope-#{Time.now.to_i}-#{Process.pid}"
+        js_path = File.join(Dir.tmpdir, "#{file_prefix}.js")
+        File.write(js_path, js_source)
+
+        url_to_open = "file://#{File.expand_path(bundled_index_html)}#localProfilePath=#{js_path}"
+
+        # See https://github.com/jlfwong/speedscope/blob/3613918de0dd55a263d0d04f85b0c8c2039c7bee/bin/cli.mjs#L96-L105
+        host_os = RbConfig::CONFIG["host_os"]
+        if host_os =~ /mswin|mingw|cygwin/ || host_os =~ /darwin/
+          html_path = File.join(Dir.tmpdir, "#{file_prefix}.html")
+          File.write(html_path, "<script>window.location=#{url_to_open.inspect}</script>")
+          url_to_open = "file://#{html_path}"
+        end
+
+        system os_open_command, url_to_open
+      end
+
+      def os_open_command
+        case host_os = RbConfig::CONFIG["host_os"]
+        when /mswin|mingw|cygwin/
+          "start"
+        when /darwin/
+          "open"
+        when /linux|bsd/
+          "xdg-open"
+        else
+          raise "Unsupported OS to open browser: #{host_os}"
+        end
+      end
+    end
+  end
+end
diff --git a/singed.gemspec b/singed.gemspec
index 56936ea..04f9c98 100644
--- a/singed.gemspec
+++ b/singed.gemspec
@@ -16,13 +16,10 @@ Gem::Specification.new do |spec|
     "homepage_uri" => "https://github.com/rubyatscale/singed"
   }
 
-  spec.files = Dir["README.md", "*.gemspec", "lib/**/*", "exe/**/*"]
+  spec.files = Dir["README.md", "*.gemspec", "lib/**/*", "exe/**/*", "vendor/speedscope/**/*"]
   spec.bindir = "exe"
   spec.executables = spec.files.grep(%r{\Aexe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
   spec.add_dependency "stackprof", ">= 0.2.13"
-
-  spec.add_development_dependency "rake", "~> 13.0"
-  spec.add_development_dependency "rspec"
 end
diff --git a/spec/singed/speedscope_spec.rb b/spec/singed/speedscope_spec.rb
new file mode 100644
index 0000000..ee292a8
--- /dev/null
+++ b/spec/singed/speedscope_spec.rb
@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+require "tempfile"
+
+RSpec.describe Singed::Speedscope do
+  describe ".open" do
+    let(:profile_path) do
+      Tempfile.new(["profile", ".json"]).tap do |file|
+        file.write("{}")
+        file.flush
+      end.path
+    end
+
+    context "when bundled speedscope exists" do
+      before do
+        allow(File).to receive(:exist?).with(described_class.bundled_index_html).and_return(true)
+      end
+
+      it "opens with bundled speedscope" do
+        allow(described_class).to receive(:system).and_return(true)
+
+        described_class.open(profile_path)
+
+        expect(described_class).to have_received(:system).with(described_class.send(:os_open_command), %r{\Afile://})
+      end
+    end
+
+    context "when bundled speedscope does not exist" do
+      before do
+        allow(File).to receive(:exist?).with(described_class.bundled_index_html).and_return(false)
+      end
+
+      it "opens with npx speedscope" do
+        allow(described_class).to receive(:system).and_return(true)
+
+        described_class.open(profile_path)
+
+        expect(described_class).to have_received(:system).with("npx", "speedscope", profile_path)
+      end
+    end
+  end
+
+  describe ".os_open_command" do
+    it "returns a command and does not raise" do
+      expect { described_class.send(:os_open_command) }.not_to raise_error
+      expect(described_class.send(:os_open_command)).to match(/\A(start|open|xdg-open)\z/)
+    end
+
+    context "when host_os is stubbed" do
+      subject { described_class.send(:os_open_command) }
+
+      before do
+        allow(RbConfig::CONFIG).to receive(:[]).with("host_os").and_return(stubbed_os)
+      end
+
+      context "on Windows" do
+        let(:stubbed_os) { "mingw32" }
+
+        it { is_expected.to eq("start") }
+      end
+
+      context "on MacOS" do
+        let(:stubbed_os) { "darwin22.0" }
+
+        it { is_expected.to eq("open") }
+      end
+
+      context "on Linux" do
+        let(:stubbed_os) { "linux-gnu" }
+
+        it { is_expected.to eq("xdg-open") }
+      end
+
+      context "on unsupported OS" do
+        let(:stubbed_os) { "unknown-os" }
+
+        it "raises error" do
+          expect { subject }.to raise_error(RuntimeError, /unknown-os/)
+        end
+      end
+    end
+  end
+end