WordPress REST API error

WordPress REST API rest_no_route.

This error means WordPress REST routing did not find a route that matches the namespace, path, and HTTP method you requested.

Failure stage

WordPress reached: the request hit REST routing.

Failed first: route lookup did not match namespace, path, plugin registration, or method.

Not reached yet: authentication, permission callback, and route callback logic.

Route lookup matrix

Evidence	Likely cause	First check
`rest_no_route` with correct domain	Namespace/path mismatch	Compare the URL to the registered namespace and route.
GET works, POST returns `rest_no_route`	Method mismatch	Confirm the route registered POST, not only GET.
Custom plugin route missing	Plugin inactive or registration hook wrong	Register routes on `rest_api_init`.
`/wp-json/` homepage works, route fails	Specific endpoint absent	Inspect the REST index for the namespace.
Pretty route fails, query route works	Rewrite/permalink issue	Test `?rest_route=/namespace/v1/path`.

Bad route pattern

URL called:
/wp-json/myplugin/v1/save

Route registered:
register_rest_route('my-plugin/v1', '/save', ...)

The missing dash in the namespace is enough to make WordPress return rest_no_route.

Corrected pattern

// Pattern to verify in your environment.
add_action('rest_api_init', function () {
    register_rest_route('my-plugin/v1', '/save', [
        'methods' => 'POST',
        'callback' => 'my_plugin_save',
        'permission_callback' => function () {
            return current_user_can('edit_posts');
        },
    ]);
});

POST /wp-json/my-plugin/v1/save