diff --git a/Sources/App/Views/ValidateSPIManifest/ValidateSPIManifest+View.swift b/Sources/App/Views/ValidateSPIManifest/ValidateSPIManifest+View.swift
index 57c7e4639..567bd3394 100644
--- a/Sources/App/Views/ValidateSPIManifest/ValidateSPIManifest+View.swift
+++ b/Sources/App/Views/ValidateSPIManifest/ValidateSPIManifest+View.swift
@@ -66,7 +66,8 @@ extension ValidateSPIManifest {
                                         .name("manifest"),
                                         .autofocus(true),
                                         .rows(15),
-                                        .text(model.manifest)
+                                        .text(model.manifest),
+                                        .attribute(named: "maxlength", value: "\(SPIManifest.Manifest.maxByteSize)")
                                     )
                                 ),
                                 .button(
diff --git a/Tests/AppTests/__Snapshots__/WebpageSnapshotTests/test_ValidateSPIManifest_show.1.html b/Tests/AppTests/__Snapshots__/WebpageSnapshotTests/test_ValidateSPIManifest_show.1.html
index 69d55ea72..27f4383d3 100644
--- a/Tests/AppTests/__Snapshots__/WebpageSnapshotTests/test_ValidateSPIManifest_show.1.html
+++ b/Tests/AppTests/__Snapshots__/WebpageSnapshotTests/test_ValidateSPIManifest_show.1.html
@@ -79,7 +79,7 @@ <h2 class="trimmed">Validate a Swift Package Index manifest</h2>
               <p>Enter the contents of a 
                 <code>.spi.yml</code> file for validation:
               </p>
-              <textarea name="manifest" autofocus rows="15">version: 1
+              <textarea name="manifest" autofocus rows="15" maxlength="1000">version: 1
 builder:
   configs:
     - documentation_targets: [Target1, Target2]</textarea>