If the number of route segments is unknown, you can use rest syntax — for example you might implement GitHub’s file viewer like so...
/[org]/[repo]/tree/[branch]/[...file]
...in which case a request for /sveltejs/kit/tree/main/documentation/docs/04-advanced-routing.md would result in the following parameters being available to the page:
src/routes/a/[...rest]/z/+page.svelte will match /a/z (i.e. there’s no parameter at all) as well as /a/b/z and /a/b/c/z and so on. Make sure you check that the value of the rest parameter is valid, for example using a matcher.
404 pages
Rest parameters also allow you to render custom 404s. Given these routes...
...the marx-brothers/+error.svelte file will not be rendered if you visit /marx-brothers/karl, because no route was matched. If you want to render the nested error page, you should create a route that matches any /marx-brothers/* request, and return a 404 from it:
Throws an error with a HTTP status code and an optional message.
When called during request handling, this will cause SvelteKit to
return an error response; the error will be passed to handleError as an expected error.
Make sure you're not catching the thrown error, which would prevent SvelteKit from handling it.
Throws an error with a HTTP status code and an optional message.
When called during request handling, this will cause SvelteKit to
return an error response; the error will be passed to handleError as an expected error.
Make sure you're not catching the thrown error, which would prevent SvelteKit from handling it.
Throws an error with a HTTP status code and an optional message.
When called during request handling, this will cause SvelteKit to
return an error response; the error will be passed to handleError as an expected error.
Make sure you're not catching the thrown error, which would prevent SvelteKit from handling it.
Throws an error with a HTTP status code and an optional message.
When called during request handling, this will cause SvelteKit to
return an error response; the error will be passed to handleError as an expected error.
Make sure you're not catching the thrown error, which would prevent SvelteKit from handling it.
If you don’t handle 404 cases, they will appear in handleError as framework errors, with kind: 'framework'. Otherwise, they will appear with kind: 'app'.
Optional parameters
A route like [lang]/home contains a parameter named lang which is required. Sometimes it’s beneficial to make these parameters optional, so that in this example both home and en/home point to the same page. You can do that by wrapping the parameter in another bracket pair: [[lang]]/home
Note that an optional route parameter cannot follow a rest parameter ([...rest]/[[optional]]), since parameters are matched ‘greedily’ and the optional parameter would always be unused.
Matching
A route like src/routes/fruits/[page] would match /fruits/apple, but it would also match /fruits/rocketship. We don’t want that. You can ensure that route parameters are well-formed by adding a matcher to your src/params.js file (or src/params.ts)...
If the pathname doesn’t match, SvelteKit will try to match other routes (using the sort order specified below), before eventually returning a 404. If it does match, the returned value is passed as the param value.
If validation fails, the route does not match. If it succeeds, the param is typed with the output type of the schema, which must extend string, boolean, number (as in the example above) or bigint:
The parameters of the current page - e.g. for a route like /blog/[slug], a { slug: string } object
}){consolenamespaceconsolevarconsole:Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');// Prints: hello world, to stdoutconsole.log('hello %s','world');// Prints: hello world, to stdoutconsole.error(newError('Whoops, something bad happened'));// Prints error message and stack trace to stderr:// Error: Whoops, something bad happened// at [eval]:5:15// at Script.runInThisContext (node:vm:132:18)// at Object.runInThisContext (node:vm:309:38)// at node:internal/process/execution:77:19// at [eval]-wrapper:6:22// at evalScript (node:internal/process/execution:76:60)// at node:internal/main/eval_string:23:3constname='Will Robinson';console.warn(`Danger${name}! Danger!`);// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();consterr=getStreamSomehow();constmyConsole=newconsole.Console(out,err);myConsole.log('hello world');// Prints: hello world, to outmyConsole.log('hello %s','world');// Prints: hello world, to outmyConsole.error(newError('Whoops, something bad happened'));// Prints: [Error: Whoops, something bad happened], to errconstname='Will Robinson';myConsole.warn(`Danger${name}! Danger!`);// Prints: Danger Will Robinson! Danger!, to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
constcount=5;console.log('count: %d',count);// Prints: count: 5, to stdoutconsole.log('count:',count);// Prints: count: 5, to stdout
The parameters of the current page - e.g. for a route like /blog/[slug], a { slug: string } object
})=>{consolenamespaceconsolevarconsole:Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');// Prints: hello world, to stdoutconsole.log('hello %s','world');// Prints: hello world, to stdoutconsole.error(newError('Whoops, something bad happened'));// Prints error message and stack trace to stderr:// Error: Whoops, something bad happened// at [eval]:5:15// at Script.runInThisContext (node:vm:132:18)// at Object.runInThisContext (node:vm:309:38)// at node:internal/process/execution:77:19// at [eval]-wrapper:6:22// at evalScript (node:internal/process/execution:76:60)// at node:internal/main/eval_string:23:3constname='Will Robinson';console.warn(`Danger${name}! Danger!`);// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();consterr=getStreamSomehow();constmyConsole=newconsole.Console(out,err);myConsole.log('hello world');// Prints: hello world, to outmyConsole.log('hello %s','world');// Prints: hello world, to outmyConsole.error(newError('Whoops, something bad happened'));// Prints: [Error: Whoops, something bad happened], to errconstname='Will Robinson';myConsole.warn(`Danger${name}! Danger!`);// Prints: Danger Will Robinson! Danger!, to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
constcount=5;console.log('count: %d',count);// Prints: count: 5, to stdoutconsole.log('count:',count);// Prints: count: 5, to stdout
The parameters of the current page - e.g. for a route like /blog/[slug], a { slug: string } object
.idany);// 'number'};
Transformations should be symmetrical — if converting to a number, then calling toString() on that number should return the original string. This allows the resolve function to construct a pathname correctly:
Resolve a pathname by prefixing it with the base path, if any, or resolve a route ID by populating dynamic segments with parameters.
In hash routing mode, the returned URL starts with #.
During server rendering, the base path is relative and depends on the page currently being rendered.
import{resolve}from'$app/paths';// using a pathnameconstresolved=resolve(`blog/hello-world`);// using a route ID plus parametersconstresolved=resolve('/blog/[slug]',{slug:'hello-world'});
Resolve a pathname by prefixing it with the base path, if any, or resolve a route ID by populating dynamic segments with parameters.
In hash routing mode, the returned URL starts with #.
During server rendering, the base path is relative and depends on the page currently being rendered.
import{resolve}from'$app/paths';// using a pathnameconstresolved=resolve(`blog/hello-world`);// using a route ID plus parametersconstresolved=resolve('/blog/[slug]',{slug:'hello-world'});
Matchers run both on the server and in the browser.
Prior to SvelteKit 3, you had to define each param matcher in a separate file, all listed under a params folder (for example src/params/foo.js with export const match = (param) => param === 'foo';), and matching was determined by whether or not the matcher returns a truthy value (which means no value transformation took place).
Sorting
It’s possible for multiple routes to match a given path. For example each of these routes would match /foo-abc:
SvelteKit needs to know which route is being requested. To do so, it sorts them according to the following rules...
More specific routes are higher priority (e.g. a route with no parameters is more specific than a route with one dynamic parameter, and so on)
Parameters with matchers ([name=type]) are higher priority than those without ([name])
[[optional]] and [...rest] parameters are ignored unless they are the final part of the route, in which case they are treated with lowest priority. In other words x/[[y]]/z is treated equivalently to x/z for the purposes of sorting
Ties are resolved alphabetically
...resulting in this ordering, meaning that /foo-abc will invoke src/routes/foo-abc/+page.svelte, and /foo-def will invoke src/routes/foo-[c]/+page.svelte rather than less specific routes:
Some characters can’t be used on the filesystem — / on Linux and Mac, \ / : * ? " < > | on Windows. The # and % characters have special meaning in URLs, and the [ ] ( ) characters have special meaning to SvelteKit, so these also can’t be used directly as part of your route.
To use these characters in your routes, you can use hexadecimal escape sequences, which have the format [x+nn] where nn is a hexadecimal character code:
\ — [x+5c]
/ — [x+2f]
: — [x+3a]
* — [x+2a]
? — [x+3f]
" — [x+22]
< — [x+3c]
> — [x+3e]
| — [x+7c]
# — [x+23]
% — [x+25]
[ — [x+5b]
] — [x+5d]
( — [x+28]
) — [x+29]
For example, to create a /smileys/:-) route, you would create a src/routes/smileys/[x+3a]-[x+29]/+page.svelte file.
You can determine the hexadecimal code for a character with JavaScript:
Specifies a radix for converting numeric values to strings. This value is only used for numbers.
(16);// '3a', hence '[x+3a]'
You can also use Unicode escape sequences. Generally you won’t need to as you can use the unencoded character directly, but if — for some reason — you can’t have a filename with an emoji in it, for example, then you can use the escaped characters. In other words, these are equivalent:
The format for a Unicode escape sequence is [u+nnnn] where nnnn is a valid value between 0000 and 10ffff. (Unlike JavaScript string escaping, there’s no need to use surrogate pairs to represent code points above ffff.) To learn more about Unicode encodings, consult Programming with Unicode.
Since TypeScript struggles with directories with a leading . character, you may find it useful to encode these characters when creating e.g. .well-known routes: src/routes/[x+2e]well-known/...
Advanced layouts
By default, the layout hierarchy mirrors the route hierarchy. In some cases, that might not be what you want.
(group)
Perhaps you have some routes that are ‘app’ routes that should have one layout (e.g. /dashboard or /item), and others that are ‘marketing’ routes that should have a different layout (/about or /testimonials). We can group these routes with a directory whose name is wrapped in parentheses — unlike normal directories, (app) and (marketing) do not affect the URL pathname of the routes inside them:
You can also put a +page directly inside a (group), for example if / should be an (app) or a (marketing) page.
Breaking out of layouts
The root layout applies to every page of your app — if omitted, it defaults to {@render children()}. If you want some pages to have a different layout hierarchy than the rest, then you can put your entire app inside one or more groups except the routes that should not inherit the common layouts.
In the example above, the /admin route does not inherit either the (app) or (marketing) layouts.
+page@
Pages can break out of the current layout hierarchy on a route-by-route basis. Suppose we have an /item/[id]/embed route inside the (app) group from the previous example:
Ordinarily, this would inherit the root layout, the (app) layout, the item layout and the [id] layout. We can reset to one of those layouts by appending @ followed by the segment name — or, for the root layout, the empty string. In this example, we can choose from the following options:
+page@[id].svelte - inherits from src/routes/(app)/item/[id]/+layout.svelte
+page@item.svelte - inherits from src/routes/(app)/item/+layout.svelte
+page@(app).svelte - inherits from src/routes/(app)/+layout.svelte
+page@.svelte - inherits from src/routes/+layout.svelte
Like pages, layouts can themselves break out of their parent layout hierarchy, using the same technique. For example, a +layout@.svelte component would reset the hierarchy for all its child routes.
Not all use cases are suited for layout grouping, nor should you feel compelled to use them. It might be that your use case would result in complex (group) nesting, or that you don’t want to introduce a (group) for a single outlier. It’s perfectly fine to use other means such as composition (reusable load functions or Svelte components) or if-statements to achieve what you want. The following example shows a layout that rewinds to the root layout and reuses components and functions that other layouts can also use: