Limitations and Solutions for Using PUT Method in HTML Forms

HTML Form Method Limitations

According to the W3C HTML standard specification, the method attribute of HTML forms only supports two valid values: get and post. This means developers cannot directly use syntax like <form method="put"> to send PUT requests. When browsers encounter invalid method values, they default to treating them as GET requests.

Historical Context of Standard Specifications

While HTML is closely tied to the HTTP protocol, HTML forms have never supported the complete set of HTTP methods. Early HTML5 drafts did include support for PUT and DELETE methods, with Mozilla even implementing this functionality in Firefox beta versions. However, these methods were subsequently removed from the final specification during the standardization process.

Technical Considerations for Removing PUT and DELETE

The W3C discussion on this issue raised several key technical considerations. First, using PUT method for form submission presents semantic contradictions—PUT typically replaces entire resources, while form submissions often only update partial resource attributes. Second, DELETE method only makes sense without payload, which conflicts with forms that typically contain submitted data.

Practical Development Solutions

Despite the lack of standard support, modern web development still requires RESTful-style API calls. A common solution involves using POST method as a tunnel, passing the actual HTTP method through hidden fields:

<form method="post" action="/resource">
  <input type="hidden" name="_method" value="put" />
  <input type="text" name="name" value="Example" />
  <button type="submit">Update Resource</button>
</form>

This approach requires corresponding parsing on the server side, with many popular web frameworks (such as Ruby on Rails, Laravel, etc.) providing built-in support for this pattern.

Technical Implications and Best Practices

While using POST to simulate PUT operations addresses functional requirements, it introduces several technical challenges. For instance, POST responses can be cached, whereas PUT responses typically should not be cached, potentially leading to cache inconsistencies. Additionally, using non-idempotent POST methods to perform idempotent PUT operations complicates recovery from network failures.

In practical development, it's recommended that developers clearly understand these technical limitations and choose appropriate solutions based on project requirements. For applications requiring full RESTful support, consider using JavaScript with XMLHttpRequest or Fetch API to directly send PUT requests, thus avoiding form method limitations.