diff --git a/pkg/cmd/pr/diff/diff.go b/pkg/cmd/pr/diff/diff.go
index b7ef11707..decfeb478 100644
--- a/pkg/cmd/pr/diff/diff.go
+++ b/pkg/cmd/pr/diff/diff.go
@@ -11,8 +11,10 @@ import (
 
 	"github.com/MakeNowJust/heredoc"
 	"github.com/cli/cli/v2/api"
+	"github.com/cli/cli/v2/internal/browser"
 	"github.com/cli/cli/v2/internal/ghinstance"
 	"github.com/cli/cli/v2/internal/ghrepo"
+	"github.com/cli/cli/v2/internal/text"
 	"github.com/cli/cli/v2/pkg/cmd/pr/shared"
 	"github.com/cli/cli/v2/pkg/cmdutil"
 	"github.com/cli/cli/v2/pkg/iostreams"
@@ -22,6 +24,7 @@ import (
 type DiffOptions struct {
 	HttpClient func() (*http.Client, error)
 	IO         *iostreams.IOStreams
+	Browser    browser.Browser
 
 	Finder shared.PRFinder
 
@@ -29,12 +32,14 @@ type DiffOptions struct {
 	UseColor    bool
 	Patch       bool
 	NameOnly    bool
+	BrowserMode bool
 }
 
 func NewCmdDiff(f *cmdutil.Factory, runF func(*DiffOptions) error) *cobra.Command {
 	opts := &DiffOptions{
 		IO:         f.IOStreams,
 		HttpClient: f.HttpClient,
+		Browser:    f.Browser,
 	}
 
 	var colorFlag string
@@ -46,7 +51,9 @@ func NewCmdDiff(f *cmdutil.Factory, runF func(*DiffOptions) error) *cobra.Comman
 			View changes in a pull request. 
 
 			Without an argument, the pull request that belongs to the current branch
-			is selected.			
+			is selected.
+			
+			With '--web', open the pull request diff in a web browser instead.
 		`),
 		Args: cobra.MaximumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
@@ -81,6 +88,7 @@ func NewCmdDiff(f *cmdutil.Factory, runF func(*DiffOptions) error) *cobra.Comman
 	cmdutil.StringEnumFlag(cmd, &colorFlag, "color", "", "auto", []string{"always", "never", "auto"}, "Use color in diff output")
 	cmd.Flags().BoolVar(&opts.Patch, "patch", false, "Display diff in patch format")
 	cmd.Flags().BoolVar(&opts.NameOnly, "name-only", false, "Display only names of changed files")
+	cmd.Flags().BoolVarP(&opts.BrowserMode, "web", "w", false, "Open the pull request diff in the browser")
 
 	return cmd
 }
@@ -90,11 +98,24 @@ func diffRun(opts *DiffOptions) error {
 		Selector: opts.SelectorArg,
 		Fields:   []string{"number"},
 	}
+
+	if opts.BrowserMode {
+		findOptions.Fields = []string{"url"}
+	}
+
 	pr, baseRepo, err := opts.Finder.Find(findOptions)
 	if err != nil {
 		return err
 	}
 
+	if opts.BrowserMode {
+		openUrl := fmt.Sprintf("%s/files", pr.URL)
+		if opts.IO.IsStdoutTTY() {
+			fmt.Fprintf(opts.IO.ErrOut, "Opening %s in your browser.\n", text.DisplayURL(openUrl))
+		}
+		return opts.Browser.Browse(openUrl)
+	}
+
 	httpClient, err := opts.HttpClient()
 	if err != nil {
 		return err
diff --git a/pkg/cmd/pr/diff/diff_test.go b/pkg/cmd/pr/diff/diff_test.go
index af0256e5b..bb8eb87bf 100644
--- a/pkg/cmd/pr/diff/diff_test.go
+++ b/pkg/cmd/pr/diff/diff_test.go
@@ -9,12 +9,12 @@ import (
 	"testing"
 
 	"github.com/cli/cli/v2/api"
+	"github.com/cli/cli/v2/internal/browser"
 	"github.com/cli/cli/v2/internal/ghrepo"
 	"github.com/cli/cli/v2/pkg/cmd/pr/shared"
 	"github.com/cli/cli/v2/pkg/cmdutil"
 	"github.com/cli/cli/v2/pkg/httpmock"
 	"github.com/cli/cli/v2/pkg/iostreams"
-	"github.com/google/go-cmp/cmp"
 	"github.com/google/shlex"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -92,6 +92,16 @@ func Test_NewCmdDiff(t *testing.T) {
 			isTTY:   true,
 			wantErr: "invalid argument \"doublerainbow\" for \"--color\" flag: valid values are {always|never|auto}",
 		},
+		{
+			name:  "web mode",
+			args:  "123 --web",
+			isTTY: true,
+			want: DiffOptions{
+				SelectorArg: "123",
+				UseColor:    true,
+				BrowserMode: true,
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -130,19 +140,22 @@ func Test_NewCmdDiff(t *testing.T) {
 
 			assert.Equal(t, tt.want.SelectorArg, opts.SelectorArg)
 			assert.Equal(t, tt.want.UseColor, opts.UseColor)
+			assert.Equal(t, tt.want.BrowserMode, opts.BrowserMode)
 		})
 	}
 }
 
 func Test_diffRun(t *testing.T) {
-	pr := &api.PullRequest{Number: 123}
+	pr := &api.PullRequest{Number: 123, URL: "https://github.com/OWNER/REPO/pull/123"}
 
 	tests := []struct {
-		name       string
-		opts       DiffOptions
-		rawDiff    string
-		wantAccept string
-		wantStdout string
+		name           string
+		opts           DiffOptions
+		wantFields     []string
+		wantStdout     string
+		wantStderr     string
+		wantBrowsedURL string
+		httpStubs      func(*httpmock.Registry)
 	}{
 		{
 			name: "no color",
@@ -151,9 +164,11 @@ func Test_diffRun(t *testing.T) {
 				UseColor:    false,
 				Patch:       false,
 			},
-			rawDiff:    fmt.Sprintf(testDiff, "", "", "", ""),
-			wantAccept: "application/vnd.github.v3.diff",
+			wantFields: []string{"number"},
 			wantStdout: fmt.Sprintf(testDiff, "", "", "", ""),
+			httpStubs: func(reg *httpmock.Registry) {
+				stubDiffRequest(reg, "application/vnd.github.v3.diff", fmt.Sprintf(testDiff, "", "", "", ""))
+			},
 		},
 		{
 			name: "with color",
@@ -162,9 +177,11 @@ func Test_diffRun(t *testing.T) {
 				UseColor:    true,
 				Patch:       false,
 			},
-			rawDiff:    fmt.Sprintf(testDiff, "", "", "", ""),
-			wantAccept: "application/vnd.github.v3.diff",
+			wantFields: []string{"number"},
 			wantStdout: fmt.Sprintf(testDiff, "\x1b[m", "\x1b[1;38m", "\x1b[32m", "\x1b[31m"),
+			httpStubs: func(reg *httpmock.Registry) {
+				stubDiffRequest(reg, "application/vnd.github.v3.diff", fmt.Sprintf(testDiff, "", "", "", ""))
+			},
 		},
 		{
 			name: "patch format",
@@ -173,9 +190,11 @@ func Test_diffRun(t *testing.T) {
 				UseColor:    false,
 				Patch:       true,
 			},
-			rawDiff:    fmt.Sprintf(testDiff, "", "", "", ""),
-			wantAccept: "application/vnd.github.v3.patch",
+			wantFields: []string{"number"},
 			wantStdout: fmt.Sprintf(testDiff, "", "", "", ""),
+			httpStubs: func(reg *httpmock.Registry) {
+				stubDiffRequest(reg, "application/vnd.github.v3.patch", fmt.Sprintf(testDiff, "", "", "", ""))
+			},
 		},
 		{
 			name: "name only",
@@ -185,51 +204,51 @@ func Test_diffRun(t *testing.T) {
 				Patch:       false,
 				NameOnly:    true,
 			},
-			rawDiff:    fmt.Sprintf(testDiff, "", "", "", ""),
-			wantAccept: "application/vnd.github.v3.diff",
+			wantFields: []string{"number"},
 			wantStdout: ".github/workflows/releases.yml\nMakefile\n",
+			httpStubs: func(reg *httpmock.Registry) {
+				stubDiffRequest(reg, "application/vnd.github.v3.diff", fmt.Sprintf(testDiff, "", "", "", ""))
+			},
+		},
+		{
+			name: "web mode",
+			opts: DiffOptions{
+				SelectorArg: "123",
+				BrowserMode: true,
+			},
+			wantFields:     []string{"url"},
+			wantStderr:     "Opening github.com/OWNER/REPO/pull/123/files in your browser.\n",
+			wantBrowsedURL: "https://github.com/OWNER/REPO/pull/123/files",
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			httpReg := &httpmock.Registry{}
 			defer httpReg.Verify(t)
-
-			var gotAccept string
-			httpReg.Register(
-				httpmock.REST("GET", "repos/OWNER/REPO/pulls/123"),
-				func(req *http.Request) (*http.Response, error) {
-					gotAccept = req.Header.Get("Accept")
-					return &http.Response{
-						StatusCode: 200,
-						Request:    req,
-						Body:       io.NopCloser(strings.NewReader(tt.rawDiff)),
-					}, nil
-				})
-
-			opts := tt.opts
-			opts.HttpClient = func() (*http.Client, error) {
+			if tt.httpStubs != nil {
+				tt.httpStubs(httpReg)
+			}
+			tt.opts.HttpClient = func() (*http.Client, error) {
 				return &http.Client{Transport: httpReg}, nil
 			}
 
-			ios, _, stdout, stderr := iostreams.Test()
-			opts.IO = ios
-			finder := shared.NewMockFinder("123", pr, ghrepo.New("OWNER", "REPO"))
-			finder.ExpectFields([]string{"number"})
-			opts.Finder = finder
+			browser := &browser.Stub{}
+			tt.opts.Browser = browser
 
-			if err := diffRun(&opts); err != nil {
-				t.Fatalf("unexpected error: %s", err)
-			}
-			if diff := cmp.Diff(tt.wantStdout, stdout.String()); diff != "" {
-				t.Errorf("command output did not match:\n%s", diff)
-			}
-			if stderr.String() != "" {
-				t.Errorf("unexpected stderr output: %s", stderr.String())
-			}
-			if gotAccept != tt.wantAccept {
-				t.Errorf("unexpected Accept header: %s", gotAccept)
-			}
+			ios, _, stdout, stderr := iostreams.Test()
+			ios.SetStdoutTTY(true)
+			tt.opts.IO = ios
+
+			finder := shared.NewMockFinder("123", pr, ghrepo.New("OWNER", "REPO"))
+			finder.ExpectFields(tt.wantFields)
+			tt.opts.Finder = finder
+
+			err := diffRun(&tt.opts)
+			assert.NoError(t, err)
+
+			assert.Equal(t, tt.wantStdout, stdout.String())
+			assert.Equal(t, tt.wantStderr, stderr.String())
+			assert.Equal(t, tt.wantBrowsedURL, browser.BrowsedURL())
 		})
 	}
 }
@@ -349,3 +368,23 @@ func Test_changedFileNames(t *testing.T) {
 		}
 	}
 }
+
+func stubDiffRequest(reg *httpmock.Registry, accept, diff string) {
+	reg.Register(
+		func(req *http.Request) bool {
+			if !strings.EqualFold(req.Method, "GET") {
+				return false
+			}
+			if req.URL.EscapedPath() != "/repos/OWNER/REPO/pulls/123" {
+				return false
+			}
+			return req.Header.Get("Accept") == accept
+		},
+		func(req *http.Request) (*http.Response, error) {
+			return &http.Response{
+				StatusCode: 200,
+				Request:    req,
+				Body:       io.NopCloser(strings.NewReader(diff)),
+			}, nil
+		})
+}