Arcjet bot detection allows you to manage traffic by automated clients and bots.
Configuration
Bot detection is configured by specifying the bot types you wish to block and
optional user agent patterns to add or remove from the bot detection list.
The configuration definition is:
The arcjet client is configured with one or more detectBot rules which take
one or many BotOptions.
Which bots to block?
Which bot types to block is configured by listing one or more types in the
block configuration block. The types are listed on the bot
types page.
Adding bot detection rules
You can add additional bot detection rules to the patternsadd configuration
property. Each rule is a regular expression that matches the user agent of the
bot plus a label to indicate what type of bot it is from ArcjetBotTypes
described in the list of bot types. The following
example adds a rule to detect Googlebot as a LikelyAutomated bot.
Arcjet includes a set of default matching rules to detect common bots. You can
remove any of these rules by listing them in the patternsremove
configuration property:
Bot protection rules can be configured in two ways:
Per route: The rule is defined in the route handler itself. This allows
you to configure the rule alongside the code it is protecting which is useful
if you want to use the decision to add context to your own code. However, it
means rules are not located in a single place.
Hooks: The rule is defined as a hook. This allows you to
configure rules in a single place or apply them globally to all routes, but
it means the rules are not located alongside the code they are protecting.
If you use Arcjet in hooks and individual routes, you need to be careful
that Arcjet is not running multiple times per request. This can be avoided by
excluding the individual routes before running Arcjet in the hook.
For example, if you already have rules defined in the API route
at /api/arcjet, you can exclude it from the hook like this:
Decision
The quick start example will deny requests
that match the bot detection rules, immediately returning a response to the
client using SvelteKit hooks.
Arcjet also provides a single protect function that is used to execute your
protection rules. This requires a RequestEvent property which is the event
context as passed to the request handler.
This function returns a Promise that resolves to an
ArcjetDecision object. This contains the following properties:
id (string) - The unique ID for the request. This can be used to look up
the request in the Arcjet dashboard. It is prefixed with req_ for decisions
involving the Arcjet cloud API. For decisions taken locally, the prefix is
lreq_.
conclusion (ArcjetConclusion) - The final conclusion based on evaluating
each of the configured rules. If you wish to accept Arcjet’s recommended
action based on the configured rules then you can use this property.
reason (ArcjetReason) - An object containing more detailed
information about the conclusion.
results (ArcjetRuleResult[]) - An array of ArcjetRuleResult objects
containing the results of each rule that was executed.
ip (ArcjetIpDetails) - An object containing Arcjet’s analysis of the
client IP address. See IP analysis in the
SDK reference for more information.
In the code above, you will see that Arcjet also returns more information in
the decicion object about the bot type of the
client we think made the request.
Error handling
Arcjet is designed to fail open so that a service issue or misconfiguration does
not block all requests. The SDK will also time out and fail open after 500ms
when NODE_ENV is production and 1000ms otherwise. However, in most cases,
the response time will be less than 20-30ms.
If there is an error condition, Arcjet will return an
ERROR type and you can check the reason property for more information, like
accessing decision.reason.message.