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Test Options

Options control how k6 executes your test, including the number of VUs, test duration, thresholds, and more. Options can be set in multiple ways with a clear precedence order.

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Setting Options

Options can be defined in three ways (in order of precedence):
  1. Command-line flags - Highest priority
  2. Environment variables
  3. Script options - Lowest priority
export let options = {
  vus: 10,
  duration: '30s',
  thresholds: {
    http_req_duration: ['p(95)<500'],
  },
};

export default function() {
  // Test logic
}

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Basic Execution Options

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Virtual Users and Duration

The simplest way to configure a test: 
export let options = {
  vus: 10,              // Number of virtual users
  duration: '30s',      // Test duration
};

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Iterations

Run a specific number of iterations instead of time-based: 
export let options = {
  vus: 10,
  iterations: 100,      // Total iterations shared across all VUs
};
With 10 VUs and 100 iterations, each VU will execute approximately 10 iterations.

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Stages (Ramping)

Gradually ramp VUs up and down: 
export let options = {
  stages: [
    { duration: '10s', target: 5 },   // Ramp up to 5 VUs
    { duration: '5s', target: 5 },    // Stay at 5 VUs
    { duration: '5s', target: 0 },    // Ramp down to 0 VUs
  ],
};

export default function() {
  let res = http.get('http://httpbin.org/');
  check(res, { 'status is 200': (r) => r.status === 200 });
}
This creates an up-flat-down ramping profile: 
VUs
 5│     ┌─────┐
 4│    /       \
 3│   /         \
 2│  /           \
 1│ /             \
 0└──────────────────
  0s  10s  15s  20s

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Thresholds

Thresholds define pass/fail criteria for your test. If a threshold fails, k6 exits with a non-zero status code. 
import http from 'k6/http';
import { check } from 'k6';

export let options = {
  thresholds: {
    // 95th percentile response time < 500ms
    http_req_duration: ['p(95)<500'],
    
    // Max response time < 1s
    'http_req_duration{name:http://httpbin.org/post}': ['max<1000'],
    
    // 99% of requests successful
    http_req_failed: ['rate<0.01'],
    
    // 90% of checks pass
    checks: ['rate>0.9'],
    
    // Multiple conditions (all must pass)
    http_req_duration: [
      'p(95)<500',
      'p(99)<1000',
      'avg<300',
    ],
  },
};

export default function() {
  http.get('http://httpbin.org/');
  http.post('http://httpbin.org/post', {data: 'some data'});
}

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Threshold Expressions

Common threshold expressions:
ExpressionDescription
p(95)<50095th percentile < 500ms
avg<200Average < 200ms
min>100Minimum > 100ms
max<1000Maximum < 1000ms
med<250Median < 250ms
rate>0.9Success rate > 90%
count>1000Total count > 1000
Thresholds cause the test to fail when exceeded, unlike checks which only record pass/fail without affecting the test outcome.

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HTTP Options

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Request Limits

export let options = {
  rps: 100,                    // Limit to 100 requests per second
  maxRedirects: 5,             // Follow up to 5 redirects
  batch: 10,                   // Max parallel requests in batch()
  batchPerHost: 5,             // Max parallel requests per host
};

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TLS/SSL Configuration

export let options = {
  insecureSkipTLSVerify: true,           // Skip TLS verification
  tlsVersion: {
    min: 'tls1.2',
    max: 'tls1.3',
  },
  tlsCipherSuites: [
    'TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256',
    'TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384',
  ],
};

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User Agent and Headers

export let options = {
  userAgent: 'k6-load-test/1.0',
  noConnectionReuse: false,              // Reuse connections
  noVUConnectionReuse: false,            // Reuse connections across iterations
};

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Timeouts

export let options = {
  setupTimeout: '60s',           // Timeout for setup() function
  teardownTimeout: '60s',        // Timeout for teardown() function
  
  noSetup: false,                // Skip setup() function
  noTeardown: false,             // Skip teardown() function
};

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Tags

Apply tags to all metrics in the test: 
export let options = {
  tags: {
    environment: 'staging',
    team: 'backend',
    version: 'v1.2.3',
  },
};

​
System Tags

Control which system tags are included with metrics: 
export let options = {
  systemTags: [
    'status',
    'method', 
    'url',
    'name',
    'group',
    'check',
    'error',
    'error_code',
    'tls_version',
    'scenario',
    'service',
  ],
};

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DNS Configuration

export let options = {
  dns: {
    ttl: '5m',                   // DNS cache TTL
    select: 'random',            // IP selection: 'first', 'random', 'roundRobin'
    policy: 'preferIPv4',        // 'preferIPv4', 'preferIPv6', 'onlyIPv4', 'onlyIPv6', 'any'
  },
};

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Hosts Override

Map hostnames to IPs: 
export let options = {
  hosts: {
    'quickpizza.grafana.com': '1.2.3.4',
    'api.example.com': '5.6.7.8',
  },
};

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Blocked Hostnames

Prevent requests to specific hosts: 
export let options = {
  blockHostnames: [
    '*.google-analytics.com',
    'analytics.example.com',
  ],
};

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Blacklist IPs

Block requests to specific IP ranges: 
export let options = {
  blacklistIPs: [
    '10.0.0.0/8',
    '192.168.0.0/16',
  ],
};

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Discard Response Bodies

Save memory by discarding response bodies: 
export let options = {
  discardResponseBodies: true,   // Don't save response bodies
};

export default function() {
  let res = http.get('https://quickpizza.grafana.com');
  // res.body will be null when discardResponseBodies is true
  
  // Override per-request
  res = http.get('https://quickpizza.grafana.com', { 
    responseType: 'text'  // Force saving this response
  });
}

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Summary Configuration

export let options = {
  summaryTrendStats: ['avg', 'min', 'med', 'max', 'p(90)', 'p(95)', 'p(99)'],
  summaryTimeUnit: 'ms',         // Time unit for summary: 's', 'ms', 'us'
};

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Paused Mode

Start test in paused state: 
export let options = {
  paused: true,      // Start paused, resume with API or UI
};

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Minimum Iteration Duration

Enforce a minimum time per iteration: 
export let options = {
  minIterationDuration: '10s',   // Each iteration takes at least 10s
};

export let options = {
  noCookiesReset: true,          // Don't reset cookies between iterations
};

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Complete Example

Here’s a comprehensive example combining multiple options: 
import http from 'k6/http';
import { check, sleep } from 'k6';

export let options = {
  // Execution
  stages: [
    { duration: '30s', target: 20 },
    { duration: '1m', target: 20 },
    { duration: '30s', target: 0 },
  ],
  
  // Thresholds
  thresholds: {
    http_req_duration: ['p(95)<500', 'p(99)<1000'],
    http_req_failed: ['rate<0.01'],
    checks: ['rate>0.95'],
  },
  
  // HTTP
  userAgent: 'k6-load-test/1.0',
  maxRedirects: 5,
  insecureSkipTLSVerify: true,
  batch: 10,
  batchPerHost: 5,
  
  // Tags
  tags: {
    environment: 'production',
    team: 'platform',
  },
  
  // Timeouts
  setupTimeout: '60s',
  teardownTimeout: '60s',
  
  // Summary
  summaryTrendStats: ['avg', 'min', 'med', 'max', 'p(90)', 'p(95)', 'p(99)'],
};

export function setup() {
  // Setup code
  return { timestamp: Date.now() };
}

export default function(data) {
  let res = http.get('https://quickpizza.grafana.com');
  
  check(res, {
    'status is 200': (r) => r.status === 200,
    'response time < 500ms': (r) => r.timings.duration < 500,
  });
  
  sleep(1);
}

export function teardown(data) {
  console.log(`Test ran for ${Date.now() - data.timestamp}ms`);
}

​
Options Reference Table

OptionTypeDefaultDescription
vusinteger1Number of virtual users
durationstring-Test duration (e.g., ’30s’, ‘5m’)
iterationsinteger-Total iterations to execute
stagesarray-Ramping configuration
scenariosobject-Advanced execution scenarios
pausedbooleanfalseStart test in paused state
setupTimeoutstring10sSetup function timeout
teardownTimeoutstring10sTeardown function timeout
rpsinteger0Max requests per second (0=unlimited)
maxRedirectsinteger10Max HTTP redirects to follow
userAgentstringk6/…User-Agent header
batchinteger20Max parallel batch requests
batchPerHostinteger6Max parallel requests per host
insecureSkipTLSVerifybooleanfalseSkip TLS certificate verification
throwbooleanfalseThrow errors instead of logging
thresholdsobject-Pass/fail criteria
tagsobject-Tags for all metrics
systemTagsarray[…]System tags to collect
summaryTrendStatsarray[…]Stats to show in summary
discardResponseBodiesbooleanfalseDiscard HTTP response bodies
noConnectionReusebooleanfalseDisable HTTP keep-alive
noVUConnectionReusebooleanfalseClose connections between iterations
minIterationDurationstring-Minimum iteration duration
noCookiesResetbooleanfalseDon’t reset cookies per iteration

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