From cc9882e586a898552c3a178b916e2593503a8b4f Mon Sep 17 00:00:00 2001
From: Jay-Chou <42150440+at7211@users.noreply.github.com>
Date: Mon, 9 Feb 2026 23:02:01 +0800
Subject: [PATCH] docs: add errorFormat option to ValidationPipe documentation

Document the new `errorFormat` option for ValidationPipe that allows
users to choose between 'list' (default) and 'grouped' error formats.

Related to nestjs/nest#16268
---
 content/techniques/validation.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/content/techniques/validation.md b/content/techniques/validation.md
index a7f59fdc55..ab9d28cdab 100644
--- a/content/techniques/validation.md
+++ b/content/techniques/validation.md
@@ -31,6 +31,7 @@ export interface ValidationPipeOptions extends ValidatorOptions {
   transform?: boolean;
   disableErrorMessages?: boolean;
   exceptionFactory?: (errors: ValidationError[]) => any;
+  errorFormat?: 'list' | 'grouped';
 }
 ```
 
@@ -129,6 +130,11 @@ In addition to these, all `class-validator` options (inherited from the `Validat
     <td><code>boolean</code></td>
     <td>When set to true, validation of the given property will stop after encountering the first error. Defaults to false.</td>
   </tr>
+  <tr>
+    <td><code>errorFormat</code></td>
+    <td><code>'list' | 'grouped'</code></td>
+    <td>Specifies the format of validation error messages. <code>'list'</code> (default) returns an array of error message strings. <code>'grouped'</code> returns an object with property paths as keys and arrays of unmodified error messages as values, preserving custom validation messages without prepending parent path prefixes.</td>
+  </tr>
 </table>
 
 > info **Notice** Find more information about the `class-validator` package in its [repository](https://github.com/typestack/class-validator).