diff --git a/CHANGELOG.md b/CHANGELOG.md
index 571bc7d..9398430 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ### 0.4.1 (Next)
 
+* [#8](https://github.com/dblock/ruby-link-checker/issues/8): Added `protocol` configuration option to `LinkChecker::Async::HTTP` to force HTTP/1 or HTTP/2 - [@dblock](https://github.com/dblock), [@Copilot](https://github.com/Copilot).
 * Your contribution here.
 
 ### 0.4.0 (2026/8/17)
diff --git a/README.md b/README.md
index 7d93dd8..9947022 100644
--- a/README.md
+++ b/README.md
@@ -172,6 +172,14 @@ LinkChecker::Async::HTTP.configure do |config|
 end
 ```
 
+You can also force a specific HTTP protocol version, `:http1` or `:http2`, per instance or globally. By default, `async-http` negotiates the protocol version with the server.
+
+```ruby
+LinkChecker::Async::HTTP.configure do |config|
+  config.protocol = :http2
+end
+```
+
 #### [LinkChecker::Net::HTTP](lib/ruby-link-checker/net/http/checker.rb)
 
 Slow, sequential checker.
diff --git a/lib/ruby-link-checker/async/http/checker.rb b/lib/ruby-link-checker/async/http/checker.rb
index 70ee9dd..4219d99 100644
--- a/lib/ruby-link-checker/async/http/checker.rb
+++ b/lib/ruby-link-checker/async/http/checker.rb
@@ -69,13 +69,28 @@ def _queue(&block)
         def _client_for(uri)
           key = [uri.scheme, uri.host, uri.port]
           @clients[key] ||= begin
-            endpoint = ::Async::HTTP::Endpoint.parse(uri.to_s, timeout: open_timeout)
+            endpoint = ::Async::HTTP::Endpoint.parse(uri.to_s, timeout: open_timeout, **_endpoint_options)
             ::Async::HTTP::Client.new(endpoint)
           end
         end
 
         private
 
+        # Maps the configured protocol (:http1 or :http2) to the
+        # corresponding async-http protocol implementation.
+        def _endpoint_options
+          case protocol
+          when :http1
+            { protocol: ::Async::HTTP::Protocol::HTTP1 }
+          when :http2
+            { protocol: ::Async::HTTP::Protocol::HTTP2 }
+          when nil
+            {}
+          else
+            raise ArgumentError, "Unsupported protocol: #{protocol.inspect}, expected :http1 or :http2"
+          end
+        end
+
         def _flush!
           queue = @queue
           @queue = []
diff --git a/lib/ruby-link-checker/async/http/config.rb b/lib/ruby-link-checker/async/http/config.rb
index 8569257..f21d8e1 100644
--- a/lib/ruby-link-checker/async/http/config.rb
+++ b/lib/ruby-link-checker/async/http/config.rb
@@ -9,6 +9,7 @@ module Config
         ATTRIBUTES = %i[
           read_timeout
           open_timeout
+          protocol
         ].freeze
 
         attr_accessor(*Config::ATTRIBUTES)
@@ -16,6 +17,7 @@ module Config
         def reset
           self.read_timeout = nil
           self.open_timeout = nil
+          self.protocol = nil
         end
       end
 
diff --git a/spec/ruby-link-checker/async/http/checker_spec.rb b/spec/ruby-link-checker/async/http/checker_spec.rb
index 8b06f02..a0da95e 100644
--- a/spec/ruby-link-checker/async/http/checker_spec.rb
+++ b/spec/ruby-link-checker/async/http/checker_spec.rb
@@ -60,6 +60,53 @@ def check(url, options = {})
       end
     end
 
+    context 'with a protocol option', vcr: { cassette_name: '200' } do
+      before do
+        LinkChecker::Async::HTTP.configure do |config|
+          config.protocol = protocol
+        end
+        expect(Async::HTTP::Endpoint).to receive(:parse).with(
+          URI(url).to_s,
+          hash_including(protocol: expected_protocol)
+        ).and_call_original
+      end
+
+      include_context 'with url'
+
+      context 'http1' do
+        let(:protocol) { :http1 }
+        let(:expected_protocol) { Async::HTTP::Protocol::HTTP1 }
+
+        it 'creates requests using HTTP/1' do
+          expect(result.success?).to be true
+        end
+      end
+
+      context 'http2' do
+        let(:protocol) { :http2 }
+        let(:expected_protocol) { Async::HTTP::Protocol::HTTP2 }
+
+        it 'creates requests using HTTP/2' do
+          expect(result.success?).to be true
+        end
+      end
+    end
+
+    context 'with an unsupported protocol option' do
+      before do
+        LinkChecker::Async::HTTP.configure do |config|
+          config.protocol = :http3
+        end
+      end
+
+      include_context 'with url'
+
+      it 'raises an ArgumentError' do
+        expect(result.error?).to be true
+        expect(result.error.message).to eq('Unsupported protocol: :http3, expected :http1 or :http2')
+      end
+    end
+
     context 'timeout' do
       before do
         stub_request(:get, 'https://www.example.org/').to_timeout