Arcjet SvelteKit SDK reference
This is the reference guide for the Arcjet SvelteKit SDK, available on GitHub and licensed under the Apache 2.0 license.
What is Arcjet?
Arcjet helps developers protect their apps in just a few lines of code. Implement rate limiting, bot protection, email validation, and defense against common attacks.Installation
In your project root, run the following command to install the SDK:
Requirements
- Node.js 18 or later
- SvelteKit 2.5 or later
- CommonJS is not supported. Arcjet is ESM only.
Quick start
Check out the quick start guide.
Configuration
Create a new Arcjet
object with your API key and rules. This should be in a
server-only module in /src/lib/server/
.
The required fields are:
key
(string
) - Your Arcjet site key. This can be found in the SDK Installation section for the site in the Arcjet Dashboard.rules
- The rules to apply to the request. See the various sections of the docs for how to configure these e.g. shield, rate limiting, bot protection, email validation.
The optional fields are:
characteristics
(string[]
) - A list of characteristics to be used to uniquely identify clients.
Rule modes
Each rule can be configured in either LIVE
or DRY_RUN
mode. When in
DRY_RUN
mode, each rule will return its decision, but the end conclusion will
always be ALLOW
.
This allows you to run Arcjet in passive / demo mode to test rules before enabling them. Arcjet will log what it would have done.
Multiple rules
You can combine rules to create a more complex protection strategy. For example, you can combine rate limiting and bot protection rules to protect your API from automated clients.
Environment variables
The following environment variables can be used to configure the SDK at runtime:
ARCJET_BASE_URL
- Will override the decision API which the SDK communicates with. This defaults tohttps://decide.arcjet.com
and should only be changed if directed by Arcjet support.ARCJET_LOG_LEVEL
- The log level to use, eitherdebug
,info
,warn
, orerror
. Defaults towarn
. If a rule is in dry run mode, a warning will be output with the decision that would have been applied.ARCJET_ENV
- Set todevelopment
to force Arcjet into development mode. This will allow private/internal addresses so that the SDKs work correctly locally. You usually do not need to set this because it usesNODE_ENV
when set. See Troubleshooting for when this may be needed.
Custom logging
The SDK uses a lightweight logger which mirrors the Pino structured logger interface. You can use this to customize the logging output.
First, install the required packages:
Then, create a custom logger that will log to JSON in production and pretty print in development:
Protect
Arcjet provides a single protect
function that is used to execute your
protection rules. This requires a RequestEvent
object which is the event
argument as passed to the SvelteKit request handler. Rules you add to the SDK may
require additional details, such as the validateEmail
rule requiring an
additional email
prop.
This function returns a Promise
that resolves to an ArcjetDecision
object,
which provides a high-level conclusion and detailed explanations of the decision
made by Arcjet.
A good place to put this is in your app’s server hooks file:
Decision
The protect
function 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 withreq_
for decisions involving the Arcjet cloud API. For decisions taken locally, the prefix islreq_
.conclusion
("ALLOW" | "DENY" | "CHALLENGE" | "ERROR"
) - 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 ofArcjetRuleResult
objects containing the results of each rule that was executed.ttl
(uint32
) - The time-to-live for the decision in seconds. This is the time that the decision is valid for. After this time, the decision will be re-evaluated. The SDK automatically cachesDENY
decisions for the length of the TTL.ip
(ArcjetIpDetails
) - An object containing Arcjet’s analysis of the client IP address. See IP analysis below for more information.
Conclusion
The ArcjetDecision
object has the following methods that should be used to
check the conclusion:
isAllowed()
(bool
) - The request should be allowed.isDenied()
(bool
) - The request should be denied.isErrored()
(bool
) - There was an unrecoverable error.
Reason
The reason
property of the ArcjetDecision
object contains an ArcjetReason
object which provides more detailed information about the conclusion. This is
the final decision reason and is based on the configured rules.
The ArcjetReason
object has the following methods that can be used to check
which rule caused the conclusion:
isBot()
(bool
) - Returnstrue
if the bot protection rules have been applied and the request was considered to have been made by a bot.isRateLimit()
(bool
) - Returnstrue
if the rate limit rules have been applied and the request has exceeded the rate limit.isShield()
(bool
) - Returnstrue
if the shield rules have been applied and the request is suspicious based on analysis by Arcjet Shield.isEmail()
(bool
) - Returnstrue
if the email validation rules have been applied and the email address has a problem.isErrored()
(bool
) - Returnstrue
if there was an error processing the request.
Results
The results
property of the ArcjetDecision
object contains an array of
ArcjetRuleResult
objects. There will be one for each configured rule so you
can inspect the individual results:
id
(string
) - The ID of the rule result. Not yet implemented.state
(ArcjetRuleState
) - Whether the rule was executed or not.conclusion
(ArcjetConclusion
) - The conclusion of the rule. This will be one of the above conclusions:ALLOW
,DENY
,CHALLENGE
, orERROR
.reason
(ArcjetReason
) - An object containing more detailed information about the conclusion for this rule. Each rule type has its own reason object with different properties.
You can iterate through the results and check the conclusion for each rule.
This example will log the full result as well as each rate limit rule:
Rule state
The state
property of the ArcjetRuleResult
object is an ArcjetRuleState
.
Each rule is evaluated individually and can be in one of the following states:
DRY_RUN
- The rule was executed in dry run mode. This means that the rule was executed but the conclusion was not applied to the request. This is useful for testing rules before enabling them.RUN
- The rule was executed and the conclusion was applied to the request.NOT_RUN
- The rule was not executed. This can happen if another rule has already reached a conclusion that applies to the request. For example, if a rate limit rule is configured then these are evaluated before all other rules. If the client has reached the maximum number of requests then other rules will not be evaluated.CACHED
- The rule was not executed because the previous result was cached. Results are cached when the decision conclusion isDENY
. Subsequent requests from the same client will not be evaluated against the rule until the cache expires.
Rule reason
The reason
property of the ArcjetRuleResult
object contains an
ArcjetReason
object which provides more detailed information about the
conclusion for that configured rule.
Shield
The ArcjetReason
object for shield rules has the following properties:
See the shield documentation for more information about these properties.
Bot protection
The ArcjetReason
object for bot protection rules has the following properties:
Each of the allowed
and denied
arrays contains the identifiers of the bots
allowed or denied from our full list of bots.
Rate limiting
The ArcjetReason
object for rate limiting rules has the following properties:
See the rate limiting documentation for more information about these properties.
Email validation & verification
The ArcjetReason
object for email rules has the following properties:
An ArcjetEmailType
is one of the following strings:
See the email validation documentation for more information about these properties.
IP analysis
As of SDK version 1.0.0-alpha.11
, the ArcjetDecision
object contains an ip
property. This includes additional data about the client IP address:
IP location
The IP location fields may be undefined
, but you can use various methods to
check their availability. Using the methods will also refine the type to remove
the need for null or undefined checks.
hasLatitude()
(bool
): returns whether thelatitude
andaccuracyRadius
fields are available.hasLongitude()
(bool
): returns whether thelongitude
andaccuracyRadius
fields are available.hasAccuracyRadius()
(bool
): returns whether thelongitude
,latitude
, andaccuracyRadius
fields are available.hasTimezone()
(bool
): returns whether thetimezone
field is available.hasPostalCode()
(bool
): returns whether thepostalCode
field is available.hasCity()
(bool
): returns whether thecity
field is available.hasRegion()
(bool
): returns whether theregion
field is available.hasCountry()
(bool
): returns whether thecountry
andcountryName
fields are available.hasContinent()
(bool
): returns whether thecontinent
andcontinentName
fields are available.latitude
(number | undefined
): the latitude of the client IP address.longitude
(number | undefined
): the longitude of the client IP address.accuracyRadius
(number | undefined
): how accurate the location is in kilometers.timezone
(string | undefined
): the timezone of the client IP address.postalCode
(string | undefined
): the postal or zip code of the client IP address.city
(string | undefined
): the city of the client IP address.region
(string | undefined
): the region of the client IP address.country
(string | undefined
): the country code the client IP address.countryName
(string | undefined
): the country name of the client IP address.continent
(string | undefined
): the continent code of the client IP address.continentName
(string | undefined
): the continent name of the client IP address.
Location accuracy
IP geolocation can be notoriously inaccurate, especially for mobile devices,
satellite internet providers, and even just normal users. Likewise with the
specific fields like city
and region
, which can be very inaccurate. Country
is usually accurate, but there are often cases where IP addresses are
mis-located. These fields are provided for convenience e.g. suggesting a user
location, but should not be relied upon by themselves.
IP AS
This is useful for identifying the network operator of the client IP address. This is useful for understanding whether the client is likely to be automated or not, or being stricter with requests from certain networks.
The IP AS fields may be undefined
, but you can use the hasAsn()
method to
check their availability. Using this method will also refine the type to remove
the need for null-ish checks.
hasAsn()
(bool
): returns whether all of the ASN fields are available.asn
(string | undefined
): the autonomous system (AS) number of the client IP address.asnName
(string | undefined
): the name of the AS of the client IP address.asnDomain
(string | undefined
): the domain of the AS of the client IP address.asnType
('isp' | 'hosting' | 'business' | 'education'
): the type of the AS of the client IP address. Real users are more likely to be on an ISP or business network rather than a hosting provider. Education networks often have a single or small number of IP addresses even though there are many users. A common mistake is to block a single IP because of too many requests when it is a university or company network using NAT (Network Address Translation) to give many users the same IP.asnCountry
(string | undefined
): the country code of the AS of the client IP address. This is the administrative country of the AS, not necessarily the country of the client IP address.
IP type
The service
field may be undefined
, but you can use the hasService()
method to check the availability. Using this method will also refine the type to
remove the need for null-ish checks.
hasService()
(bool
): whether theservice
field is available.service
(string | undefined
): the name of the service associated with the IP address—e.g.Apple Private Relay
.isHosting()
(bool
): returns whether the IP address of the client is owned by a hosting provider. Requests originating from a hosting provider IP significantly increase the likelihood that this is an automated client.isVpn()
(bool
): returns whether the IP address of the client is owned by a VPN provider. Many people use VPNs for privacy or work purposes, so by itself this is not an indicator of the client being automated. However, it does increase the risk score of the client and depending on your use case it may be a characteristic you wish to restrict.isProxy()
(bool
): returns whether the IP address of the client is owned by a proxy provider. Similar toisVpn()
, but proxies are more likely to involve automated traffic.isTor()
(bool
): returns whether the IP address of the client is known to be part of the Tor network. As withisVpn()
, there are legitimate uses for hiding your identity through Tor, however it is also often a way to hide the origin of malicious traffic.isRelay()
(bool
): returns whether the IP address of the client is owned by a relay service. The most common example is Apple iCloud Relay, which indicates the client is less likely to be automated because Apple requires a paid subscription linked to an Apple account in good standing.
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 1000ms
when NODE_ENV
or ARCJET_ENV
is development
and 500ms 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
conclusion
.
Ad hoc rules
Sometimes it is useful to add additional protection via a rule based on the
logic in your handler; however, you usually want to inherit the rules, cache,
and other configuration from our primary SDK. This can be achieved using the
withRule
function which accepts an ad-hoc rule and can be chained to add
multiple rules. It returns an augmented client with the specialized protect
function.
IP address detection
Arcjet will automatically detect the IP address of the client making the request based on the context provided. The implementation is open source in our @arcjet/ip package.
In development environments (NODE_ENV === "development"
or
ARCJET_ENV === "development"
), we allow private/internal addresses so that the
SDKs work correctly locally.
Client override
The default client can be overridden. If no client is specified, a default one will be used. Generally you should not need to provide a client - the Arcjet SvelteKit SDK will automatically handle this for you.
Version support
Node
Arcjet supports the active and maintenance LTS versions of Node.js:
- Node.js 18.x LTS
- Node.js 20.x LTS
When a Node.js version goes end of life, we will bump the major version of the Arcjet SDK. Technical support is provided for the current major version of the Arcjet SDK for all users and for the current and previous major versions for paid users. We will provide security fixes for the current and previous major SDK versions.
SvelteKit
Arcjet supports the current major version of SvelteKit. When a new major version of SvelteKit is released, we will bump the major version of the Arcjet SDK.
- Current supported major version: SvelteKit 2.5.x
- Current supported major version: Svelte 4.2.x
Technical support is provided for the current major version of the Arcjet SDK for all users and for the current and previous major versions for paid users. We will provide security fixes for the current and previous major versions.