diff --git a/lib/docs/index.html b/lib/docs/index.html
index e60a3f960a..75c0daf797 100644
--- a/lib/docs/index.html
+++ b/lib/docs/index.html
@@ -40,6 +40,15 @@
       code a {
         color: #000000;
       }
+      .source-code {
+        display: grid;
+        grid-template-columns: auto 1fr;
+        align-items: start;
+      }
+      .source-line-numbers pre {
+        text-align: right;
+        color: #666;
+      }
       #listFields > div, #listParams > div {
         margin-bottom: 1em;
       }
@@ -429,7 +438,14 @@
     </div>
     <div id="sectSource" class="hidden">
       <h2>Source Code</h2>
-      <pre><code id="sourceText"></code></pre>
+      <div class="source-code">
+        <div class="source-line-numbers">
+          <pre><code id="sourceLineNumbers"></code></pre>
+        </div>
+        <div class="source-text">
+          <pre><code id="sourceText"></code></pre>
+        </div>
+      </div>
     </div>
     </section>
     <div id="helpDialog" class="hidden">
diff --git a/lib/docs/main.js b/lib/docs/main.js
index 71a14516cb..a9bf4a745e 100644
--- a/lib/docs/main.js
+++ b/lib/docs/main.js
@@ -50,6 +50,7 @@
     const domSectTypes = document.getElementById("sectTypes");
     const domSectValues = document.getElementById("sectValues");
     const domSourceText = document.getElementById("sourceText");
+    const domSourceLineNumbers = document.getElementById("sourceLineNumbers");
     const domStatus = document.getElementById("status");
     const domTableFnErrors = document.getElementById("tableFnErrors");
     const domTldDocs = document.getElementById("tldDocs");
@@ -238,6 +239,7 @@
         href: location.hash,
       }]);
 
+      domSourceLineNumbers.innerHTML = declLineNumbersHtml(decl_index);
       domSourceText.innerHTML = declSourceHtml(decl_index);
 
       domSectSource.classList.remove("hidden");
@@ -389,6 +391,7 @@
       if (members.length !== 0 || fields.length !== 0) {
         renderNamespace(decl_index, members, fields);
       } else {
+        domSourceLineNumbers.innerHTML = declLineNumbersHtml(decl_index);
         domSourceText.innerHTML = declSourceHtml(decl_index);
         domSectSource.classList.remove("hidden");
       }
@@ -419,6 +422,7 @@
         renderErrorSet(base_decl, errorSetNodeList(decl_index, errorSetNode));
       }
 
+      domSourceLineNumbers.innerHTML = declLineNumbersHtml(decl_index);
       domSourceText.innerHTML = declSourceHtml(decl_index);
       domSectSource.classList.remove("hidden");
     }
@@ -433,6 +437,7 @@
         domTldDocs.classList.remove("hidden");
       }
 
+      domSourceLineNumbers.innerHTML = declLineNumbersHtml(decl_index);
       domSourceText.innerHTML = declSourceHtml(decl_index);
       domSectSource.classList.remove("hidden");
     }
@@ -918,6 +923,10 @@
       return unwrapString(wasm_exports.decl_source_html(decl_index));
     }
 
+    function declLineNumbersHtml(decl_index) {
+        return unwrapString(wasm_exports.decl_line_numbers_html(decl_index));
+    }
+
     function declDoctestHtml(decl_index) {
       return unwrapString(wasm_exports.decl_doctest_html(decl_index));
     }
diff --git a/lib/docs/wasm/html_render.zig b/lib/docs/wasm/html_render.zig
index 13d2ec05c5..f88e6eb1dd 100644
--- a/lib/docs/wasm/html_render.zig
+++ b/lib/docs/wasm/html_render.zig
@@ -30,6 +30,19 @@ pub const Annotation = struct {
     dom_id: u32,
 };
 
+pub fn fileSourceLineNumbersHtml(
+    file_index: Walk.File.Index,
+    out: *std.ArrayListUnmanaged(u8),
+    root_node: Ast.Node.Index,
+) !void {
+    const ast = file_index.get_ast();
+    const first_token_line = ast.tokenLocation(0, ast.firstToken(root_node)).line;
+    const last_token_line = ast.tokenLocation(0, ast.lastToken(root_node)).line;
+    for (first_token_line..last_token_line + 1) |i| {
+        try out.print(gpa, "<span>{d}</span>\n", .{i + 1});
+    }
+}
+
 pub fn fileSourceHtml(
     file_index: Walk.File.Index,
     out: *ArrayList(u8),
diff --git a/lib/docs/wasm/main.zig b/lib/docs/wasm/main.zig
index 2a093886f5..bee3e4acbc 100644
--- a/lib/docs/wasm/main.zig
+++ b/lib/docs/wasm/main.zig
@@ -9,6 +9,7 @@ const ArrayList = std.ArrayList;
 const Writer = std.Io.Writer;
 
 const fileSourceHtml = @import("html_render.zig").fileSourceHtml;
+const fileSourceLineNumbersHtml = @import("html_render.zig").fileSourceLineNumbersHtml;
 const appendEscaped = @import("html_render.zig").appendEscaped;
 const resolveDeclLink = @import("html_render.zig").resolveDeclLink;
 const missing_feature_url_escape = @import("html_render.zig").missing_feature_url_escape;
@@ -543,6 +544,16 @@ export fn decl_fn_proto_html(decl_index: Decl.Index, linkify_fn_name: bool) Stri
     return String.init(string_result.items);
 }
 
+export fn decl_line_numbers_html(decl_index: Decl.Index) String {
+    const decl = decl_index.get();
+
+    string_result.clearRetainingCapacity();
+    fileSourceLineNumbersHtml(decl.file, &string_result, decl.ast_node) catch |err| {
+        std.debug.panic("unable to render source line numbers: {s}", .{@errorName(err)});
+    };
+    return String.init(string_result.items);
+}
+
 export fn decl_source_html(decl_index: Decl.Index) String {
     const decl = decl_index.get();