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By Divya Tagtachian in Guides & Tutorials

Creating better, more predictable redirect rules for SPAs

On Netlify, ensuring clean URLs is a matter of adding the following rule to the _redirects file:

/*   /index.html   200

This rule ensures that every path successfully resolves to index.html and the client has full control over the routing logic.

Generally, redirect rules are followed unless otherwise specified; If no conditional such as a role based or a GeoIP based redirect is present, Netlify’s proxy server adheres to all redirect rules present. Under the hood, Netlify distinguishes and categorizes redirect rules as “forced” and “unforced” for maximum granularity. Unforced rules resolves a path to a matching file. In other words, if a static file exists under the initial path being redirecting from, Netlify will serve that file in place of applying that rule.

To further illustrate this concept, let’s look at a Netlify redirects in action. Say we had the following redirect rule in our _redirects file or the equivalent redirect in our netlify.toml file:

/docs/routing/redirections /docs/routing/redirects 301
[[redirects]]
  from = "/docs/routing/redirections"
  to = "/docs/routing/redirects"
  status = 301

If Netlify finds an index.html page under the path /docs/redirections it will serve that file up in place of handling the redirect. This feature is known as file shadowing. Broadly speaking, this behavior tends to be preferred when setting up redirect rules and routing in SPAs.

In the event that you’d rather enforce the rules and explicitly redirect regardless of whether a file exists at that path or not, Netlify offers “forced” rules. Forced rules provide a way to override Netlify’s implicit file shadowing and ignore existing content that matches a path. As the name implies, forced rules always take effect no matter the scenario.

Using the above example, if Netlify finds an index.html page under the path docs/redirections it will ignore this file and instead redirect to the index.html file under /docs/redirects.

To enable forced redirects, all you’ll need to do is add a ! to the end of your redirect rule in the _redirects file or a forced=true attribute in the specific redirects portion of the netlify.toml file.

/docs/routing/redirections /docs/routing/redirects 301!
[[redirects]]
  from = "/docs/routing/redirections"
  to = "/docs/routing/redirects"
  status = 301
  force = true

Well, hasn’t this always been the case?

Despite our best efforts, this behavior hasn’t always been as predictable as we would’ve liked. Due to internal technical implementations over the last few years, the encoded conditions driving redirects changed such that forced and unforced rules did not behave as expected. This led to unpredictable, sometimes even undesired behavior where redirects were forced under certain conditions and not others.

In an effort to maintain consistency and predictability, we’ve made updates to redirects so only rules with explicit force configurations will be treated as such. This change will take effect as of April 7th.

Checkity check your redirects

Redirects are handy ways to manage how browsers identify and serve content. Mapping redirect rules accurately means that users will always have a predictable browsing experience and is key to enhancing overall user experience. With the new changes taking effect, be sure to check your site’s redirects to make sure they behave the way you expect!

To recap, here is the behavior between “forced” and “unforced” rules.

Given the following unforced redirect rule:

/docs/routing/redirections /docs/routing/redirects 301

The following file will load:

/docs/routing/redirections/index.html

Given the following forced redirect rule:

/docs/routing/redirections /docs/routing/redirects 301!

The following file will load:

/docs/routing/redirects/index.html

If you have questions about how Netlify handles redirects, be sure to check out the corresponding post related to redirects in our community forum!