Arcjet Shield protects your application against common attacks, including the
OWASP Top 10 .
Configuration
Shield is configured by specifying which mode you want it to run in.
The configuration definition is:
mode ?: " LIVE " | " DRY_RUN " ;
The arcjet
client is configured with one or more shield
rules which take
one or many ShieldOptions
.
Per route
This configures shield on a single route.
import arcjet, { shield } from " @arcjet/next " ;
import { NextResponse } from " next/server " ;
key: process . env . ARCJET_KEY !,
export async function GET ( req : Request ) {
const decision = await aj . protect (req);
if (decision . isDenied () && decision . reason . isShield ()) {
return NextResponse . json (
error: " You are suspicious! " ,
// Useful for debugging, but don't return it to the client in
//reason: decision.reason,
return NextResponse . json ({
import arcjet, { shield } from " @arcjet/next " ;
import type { NextApiRequest, NextApiResponse } from " next " ;
key: process . env . ARCJET_KEY !,
export default async function handler (
const decision = await aj . protect (req);
if (decision . isDenied () && decision . reason . isShield ()) {
return res . status ( 403 ) . json ({ error: " You are suspicious! " });
// Returning the reason is useful for debugging, but don't return it to the
// .json({ error: "You are suspicious!", reason: decision.reason });
res . status ( 200 ) . json ({ name: " Hello world " });
import arcjet, { shield } from " @arcjet/next " ;
import { NextResponse } from " next/server " ;
key: process . env . ARCJET_KEY ,
export async function GET ( req ) {
const decision = await aj . protect ( req );
if ( decision . isDenied () && decision . reason . isShield ()) {
return NextResponse . json (
error: " You are suspicious! " ,
// Useful for debugging, but don't return it to the client in
//reason: decision.reason,
return NextResponse . json ({
import arcjet, { shield } from " @arcjet/next " ;
key: process . env . ARCJET_KEY ,
export default async function handler ( req , res ) {
const decision = await aj . protect ( req );
if ( decision . isDenied () && decision . reason . isShield ()) {
return res . status ( 403 ) . json ({ error: " You are suspicious! " });
// Returning the reason is useful for debugging, but don't return it to the
// .json({ error: "You are suspicious!", reason: decision.reason });
res . status ( 200 ) . json ({ name: " Hello world " });
Middleware
This will run on every request to your Next.js app, except for static assets
(configured in the matcher
- see the Next.js
docs
for details).
Create a file called middleware.ts
in your project root (at the same level as
pages
or app
or inside src
):
import arcjet, { createMiddleware, shield } from " @arcjet/next " ;
// matcher tells Next.js which routes to run the middleware on.
// This runs the middleware on all routes except for static assets.
matcher: [ " /((?!_next/static|_next/image|favicon.ico).*) " ] ,
key: process . env . ARCJET_KEY !, // Get your site key from https://app.arcjet.com
// Protect against common attacks with Arcjet Shield
mode: " LIVE " , // will block requests. Use "DRY_RUN" to log only
// Pass any existing middleware with the optional existingMiddleware prop
export default createMiddleware (aj);
Create a file called middleware.js
in your project root (at the same level as
pages
or app
or inside src
):
import arcjet, { createMiddleware, shield } from " @arcjet/next " ;
// matcher tells Next.js which routes to run the middleware on.
// This runs the middleware on all routes except for static assets.
matcher: [ " /((?!_next/static|_next/image|favicon.ico).*) " ] ,
key: process . env . ARCJET_KEY , // Get your site key from https://app.arcjet.com
// Protect against common attacks with Arcjet Shield
mode: " LIVE " , // will block requests. Use "DRY_RUN" to log only
// Pass any existing middleware with the optional existingMiddleware prop
export default createMiddleware ( aj );
Avoiding double protection with middleware
If you use Arcjet in middleware and individual routes, you need to be careful
that Arcjet is not running multiple times per request. This can be avoided by
excluding the API route from the middleware
matcher .
For example, if you already have a shield rule defined in the API route
at /api/hello
, you can exclude it from the middleware by specifying a matcher
in /middleware.ts
:
import arcjet, { createMiddleware, shield } from " @arcjet/next " ;
// The matcher prevents the middleware executing on static assets and the
// /api/hello API route because you already installed Arcjet directly
matcher: [ " /((?!_next/static|_next/image|favicon.ico|api/hello).*) " ] ,
key: process . env . ARCJET_KEY !,
// Pass any existing middleware with the optional existingMiddleware prop
export default createMiddleware (aj);
Decision
The quick start example will deny requests
that are determined to be suspicious, immediately returning a response to the
client using Next.js middleware.
Arcjet also provides a single protect
function that is used to execute your
protection rules. This requires a request
argument which is the request
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.
See the SDK reference for more details about the
rule results.
You check if a deny conclusion has been returned by a shield rule by using
decision.isDenied()
and decision.reason.isShield()
respectively.
You can iterate through the results and check whether a shield rule was applied:
for ( const result of decision . results ) {
console . log ( " Rule Result " , result);
This example will log the full result as well as the shield rule:
Create a new API route at /app/api/route/hello.ts
:
import arcjet, { fixedWindow, shield } from " @arcjet/next " ;
import { NextResponse } from " next/server " ;
key: process . env . ARCJET_KEY !,
// Tracking by ip.src is the default if not specified
//characteristics: ["ip.src"],
export async function POST ( req : Request ) {
const decision = await aj . protect (req);
for ( const result of decision . results ) {
console . log ( " Rule Result " , result);
if (result . reason . isRateLimit ()) {
console . log ( " Rate limit rule " , result);
if (result . reason . isShield ()) {
console . log ( " Shield rule " , result);
if (decision . isDenied ()) {
return NextResponse . json ({ error: " Forbidden " } , { status: 403 });
return NextResponse . json ({
Create a new API route at /pages/api/hello.ts
:
import arcjet, { fixedWindow, shield } from " @arcjet/next " ;
import type { NextApiRequest, NextApiResponse } from " next " ;
key: process . env . ARCJET_KEY !,
// Tracking by ip.src is the default if not specified
//characteristics: ["ip.src"],
export default async function handler (
const decision = await aj . protect (req);
console . log ( " Decision " , decision);
for ( const result of decision . results ) {
console . log ( " Rule Result " , result);
if (result . reason . isRateLimit ()) {
console . log ( " Rate limit rule " , result);
if (result . reason . isShield ()) {
console . log ( " Shield rule " , result);
if (decision . isDenied ()) {
. json ({ error: " Forbidden " , reason: decision . reason });
res . status ( 200 ) . json ({ name: " Hello world " });
Create a new API route at /app/api/arcjet/route.js
:
import arcjet, { fixedWindow, shield } from " @arcjet/next " ;
import { NextResponse } from " next/server " ;
key: process . env . ARCJET_KEY ,
// Tracking by ip.src is the default if not specified
//characteristics: ["ip.src"],
export async function POST ( req ) {
const decision = await aj . protect ( req );
for ( const result of decision . results ) {
console . log ( " Rule Result " , result );
if ( result . reason . isRateLimit ()) {
console . log ( " Rate limit rule " , result );
if ( result . reason . isShield ()) {
console . log ( " Shield rule " , result );
if ( decision . isDenied ()) {
return NextResponse . json ({ error: " Forbidden " } , { status: 403 });
return NextResponse . json ({
Create a new API route at /pages/api/arcjet.js
:
import arcjet, { fixedWindow, shield } from " @arcjet/next " ;
key: process . env . ARCJET_KEY ,
// Tracking by ip.src is the default if not specified
//characteristics: ["ip.src"],
export default async function handler ( req , res ) {
const decision = await aj . protect ( req );
console . log ( " Decision " , decision );
for ( const result of decision . results ) {
console . log ( " Rule Result " , result );
if ( result . reason . isRateLimit ()) {
console . log ( " Rate limit rule " , result );
if ( result . reason . isShield ()) {
console . log ( " Shield rule " , result );
if ( decision . isDenied ()) {
. json ({ error: " Forbidden " , reason: decision . reason });
res . status ( 200 ) . json ({ name: " Hello world " });
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
type and you can check the reason
property for more information, like
accessing decision.reason.message
.
import arcjet, { shield } from " @arcjet/next " ;
import { NextResponse } from " next/server " ;
key: process . env . ARCJET_KEY !,
export async function GET ( req : Request ) {
const decision = await aj . protect (req);
if (decision . isErrored ()) {
// Fail open by logging the error and continuing
console . warn ( " Arcjet error " , decision . reason . message );
// You could also fail closed here for very sensitive routes
//return NextResponse.json({ error: "Service unavailable" }, { status: 503 });
if (decision . isDenied ()) {
return NextResponse . json (
error: " You are suspicious! " ,
// Useful for debugging, but don't return it to the client in
//reason: decision.reason,
return NextResponse . json ({
import arcjet, { shield } from " @arcjet/next " ;
import type { NextApiRequest, NextApiResponse } from " next " ;
key: process . env . ARCJET_KEY !,
export default async function handler (
const decision = await aj . protect (req);
if (decision . isErrored ()) {
// Fail open by logging the error and continuing
console . warn ( " Arcjet error " , decision . reason . message );
// You could also fail closed here for very sensitive routes
//return res.status(503).json({ error: "Service unavailable" });
if (decision . isDenied ()) {
return res . status ( 403 ) . json ({
error: " You are suspicious! " ,
res . status ( 200 ) . json ({ name: " Hello world " });
import arcjet, { shield } from " @arcjet/next " ;
import { NextResponse } from " next/server " ;
key: process . env . ARCJET_KEY ,
export async function GET ( req ) {
const decision = await aj . protect ( req );
if ( decision . isErrored ()) {
// Fail open by logging the error and continuing
console . warn ( " Arcjet error " , decision . reason . message );
// You could also fail closed here for very sensitive routes
//return NextResponse.json({ error: "Service unavailable" }, { status: 503 });
if ( decision . isDenied ()) {
return NextResponse . json (
error: " You are suspicious! " ,
// Useful for debugging, but don't return it to the client in
//reason: decision.reason,
return NextResponse . json ({
import arcjet, { shield } from " @arcjet/next " ;
key: process . env . ARCJET_KEY ,
export default async function handler ( req , res ) {
const decision = await aj . protect ( req );
if ( decision . isErrored ()) {
// Fail open by logging the error and continuing
console . warn ( " Arcjet error " , decision . reason . message );
// You could also fail closed here for very sensitive routes
//return res.status(503).json({ error: "Service unavailable" });
if ( decision . isDenied ()) {
return res . status ( 403 ) . json ({
error: " You are suspicious! " ,
res . status ( 200 ) . json ({ name: " Hello world " });
Testing
Arcjet runs the same in any environment, including locally and in CI. You can
use the mode
set to DRY_RUN
to log the results of rule execution without
blocking any requests.
We have an example test framework you can use to automatically test your rules.
Arcjet can also be triggered based using a sample of your traffic.
See the Testing section of the docs for details.
Edge Functions
Arcjet works in Edge Functions and with the Edge
Runtime .
import arcjet, { shield } from " @arcjet/next " ;
import { NextRequest, NextResponse } from " next/server " ;
key: process . env . ARCJET_KEY !,
export default async function handler ( req : NextRequest , res : NextResponse ) {
const decision = await aj . protect (req);
if (decision . isDenied ()) {
return NextResponse . json (
error: " You are suspicious! " ,
// Useful for debugging, but don't return it to the client in production
//reason: decision.reason,
return NextResponse . json ({
import arcjet, { shield } from " @arcjet/next " ;
import type { NextApiRequest, NextApiResponse } from " next " ;
key: process . env . ARCJET_KEY !,
export default async function handler (
const decision = await aj . protect (req);
if (decision . isDenied ()) {
return res . status ( 403 ) . json ({ error: " You are suspicious! " });
// Returning the reason is useful for debugging, but don't return it to the
// .json({ error: "You are suspicious!", reason: decision.reason });
res . status ( 200 ) . json ({ name: " Hello world " });
import arcjet, { shield } from " @arcjet/next " ;
import { NextResponse } from " next/server " ;
key: process . env . ARCJET_KEY ,
export async function GET ( req ) {
const decision = await aj . protect ( req );
if ( decision . isDenied ()) {
return NextResponse . json (
error: " You are suspicious! " ,
// Useful for debugging, but don't return it to the client in production
//reason: decision.reason,
return NextResponse . json ({
import arcjet, { shield } from " @arcjet/next " ;
key: process . env . ARCJET_KEY ,
export default async function handler ( req , res ) {
const decision = await aj . protect ( req );
if ( decision . isDenied ()) {
return res . status ( 403 ) . json ({ error: " You are suspicious! " });
// Returning the reason is useful for debugging, but don't return it to the
// .json({ error: "You are suspicious!", reason: decision.reason });
res . status ( 200 ) . json ({ name: " Hello world " });
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