A 409 response code tells you that a request could not be completed because of a conflict with the state of the target resource. Typically, when a 409 response code occurs, the user can resolve the conflict by merging changes or modifying the existing version of the resource.
When things are working properly, the server will generate a payload to help users recognize why the conflict is occurring. This information will be available on the back end, but should not be visible to front-end users of a website.
What Causes A 409 Error Code?
409 codes typically occur in response to PUT requests; if a third party changes the same resource you’re attempting to modify with your PUT request before the request is completed, a 409 response code may occur.
A 409 conflict error is an incredibly useful error, though it can be tedious; without a 409 conflict, you may end up overwriting other people’s edits to the requested resource. Versioning allows us to quickly detect conflicts and give you the chance to resolve them, ensuring that everyone’s edits to a resource can be checked and merged or changed before being modified.
409 Response Codes: A Practical Example
Paul, a blogger, is making edits to a blog he wrote. Unbeknownst to him, Aliza, his editor, is making edits to that very same blog. Aliza submits her edits while Paul is still working on the blog. When Paul submits his blog post, the system detects a conflict; the version of the blog that Paul is trying to modify is no longer available since the new version that Aliza edited has already been submitted.
Paul gets a message that his changes cannot be made because someone else has edited the blog. The message asks him to refresh the page and review the new version before trying again
The team’s developer sees a 409 code in the server logs. Here’s what the entry might look like:
2024-10-16 15:12:45
PUT /blog/123 HTTP/1.1
Response: 409 Conflict
Client IP: 192.168.1.101
Resource: /blog/123
Error: Conflict detected. Resource /blog/123 was modified by another process.
Client provided ETag: "abcd1234", current version: "efgh5678"
Request Data: { "name": "Paul", "email": "paul@example.com" }
The developer realizes that the CMS that the team is using doesn’t allow them to merge their edits in real-time; he starts working on a solution to solve the problem.
409 Code References
Depending on the language you’re using, you’ll use different codes to tell your server what to do in response to 409 status codes. For reference, here’s the code used to refer to 409s in some of the most common languages:
Ruby on Rails:
Go:
Symfony (PHP):
Python 2:
Python 3+:
.NET (C#):
HttpStatusCode.Conflict
Rust:
Java:
Apache HttpComponents:
Angular (TypeScript):
Node.js (JavaScript):
Django (Python):
Flask (Python):
Spring (Java):
Laravel (PHP):
Fixing 409 Response Codes
There are three steps to take in order to fix any 409 status code:
- Identify what’s causing the conflict: The error message in your server log should tell you what’s causing the conflict; that will help you understand why the conflict occurred, and how to prevent it in the future.
- Resolve the conflict: This might involve reverting back to the previous version of a resource, deleting the conflict resource, or more often than not, simply trying to update the new version of the resource.
- Try again: Once the conflict has been resolved (or you’re updating the most recent version), simply try to push through the changes again. A successful PUT request will lead to a 2xx status code, like 200 OK or 201 Created.
The Difference Between 409 & 412 Response Codes
The 409 HTTP status code and the 412 HTTP status code share many similarities; both often occur when you attempt to modify the same resource that someone else has recently modified.
Unlike 409 status codes, 412 status codes occur in response to preconditions; the code is 412 Precondition Failed (as opposed to 409 Conflict). For resources that are frequently modified, using If-Match headers is best practice; a 412 conflict will occur if the versions do not match.
412 HTTP status codes can also occur when If-None-Match preconditions fail, but these errors typically occur in very different circumstances than 409 Conflict errors.
409 Response Code Best Practices
There are a few steps you can take to minimize the impacts and reduce the rate of 409 codes:
- Use conditional logic like If-Match on resources that are frequently modified. 412 errors take fewer resources to process than a 409 Conflict error.
- Ensure that you have user-friendly messages when a client’s request cannot be completed due to a 409 Conflict. The message should tell them why the error occurred, and to refresh and try again.
- Include real-time edit merging on resources that are frequently edited by more than one person
- Use error monitoring tools like Sentry or Datadog to alert backend developers if there’s a sudden influx of 409 codes
- Use the POST HTTP request and the PUT HTTP request appropriately
How 409 Response Codes Affect SEO
A requested resource can’t be modified when the server responds with a 409 Conflict error message. This can slow down the rate at which resources are updated. Realistically, 409 response codes are typically only seen by the people who are working on a website; normal users should almost never see a 409 response code (and with best practices, they’ll only see a user-friendly message).
This means the direct impact of 409 response codes on SEO is minimal unless a problem leads to users continually seeing 409 codes. Unfortunately, 409 codes can lead to missing or inaccurate content, broken links, missing images, and more. These problems impact user experience and thus SEO.
Fortunately, search engines like Google can still crawl and index websites even when 409 errors occur. Monitoring 409 errors to ensure that there are no systemic issues, and following best practices to ensure resources are updated efficiently, are the keys to minimizing the impact 409 errors can have on user experience.
Our SEO agency can help you optimize your site; reducing the number of technical errors on your website is one of our specialties. Contact us today for a free consultation!
Jacob Kettner is the owner and CEO of First Rank Inc., a digital marketing agency based in Winnipeg, Manitoba. He currently sits on Manitoba Chamber of Commerce Small Business Advisor Council which assists people grow their small businesses in Manitoba.
