Options

Options allow you to configure how k6 will behave during test execution.

List of Options

Using Options

Options can be a part of the script code so that they can be version controlled. They can also be specified with command-line flags, environment variables or via a config file. The order of precedence is as follows:

command-line flags > environment variables > exported script options > config file > defaults

Options from each level will overwrite the options from the next level, with the command-line flags having the highest precedence.

For example, you can define the duration in 4 different ways:

• Set the duration: "10s" option in the config file
• Set the duration: "10s" option in the script
• Define K6_DURATION as an environment variable
• Use the --duration 10s command-line flag: overwrites all the above.

The following JS snippet shows how to specify options in the script:

1import http from 'k6/http';
2
3export let options = {
4  hosts: { 'test.k6.io': '1.2.3.4' },
5  stages: [
6    { duration: '1m', target: 10 },
7    { duration: '1m', target: 20 },
8    { duration: '1m', target: 0 },
9  ],
10  thresholds: { http_req_duration: ['avg<100', 'p(95)<200'] },
11  noConnectionReuse: true,
12  userAgent: 'MyK6UserAgentString/1.0',
13};
14
15export default function () {
16  http.get('http://test.k6.io/');
17}

You can also set the same options through a config file:

1{
2  "hosts": {
3    "test.k6.io": "1.2.3.4"
4  },
5  "stages": [
6    {
7      "duration": "1m",
8      "target": 10
9    },
10    {
11      "duration": "1m",
12      "target": 30
13    },
14    {
15      "duration": "1m",
16      "target": 0
17    }
18  ],
19  "thresholds": {
20    "http_req_duration": ["avg<100", "p(95)<200"]
21  },
22  "noConnectionReuse": true,
23  "userAgent": "MyK6UserAgentString/1.0"
24}

Or set some of the previous options via environment variables and command-line flags:

1$ K6_NO_CONNECTION_REUSE=true K6_USER_AGENT="MyK6UserAgentString/1.0" k6 run ~/script.js
2
3$ k6 run --no-connection-reuse --user-agent "MyK6UserAgentString/1.0" ~/script.js

Below, you'll find details on all available options that can be specified within a script. It also documents the equivalent command line flag, environment variables or option when executing k6 run ... and k6 cloud ... that can be used to override options specified in the code.

Batch

The maximum number of simultaneous/parallel connections in total that an http.batch() call in a VU can make. If you have a batch() call that you've given 20 URLs to and --batch is set to 15, then the VU will make 15 requests right away in parallel and queue the rest, executing them as soon as a previous request is done and a slot opens. Available in both the k6 run and the k6 cloud commands

1export let options = {
2  batch: 15,
3};

Batch per host

The maximum number of simultaneous/parallel connections for the same hostname that an http.batch() call in a VU can make. If you have a batch() call that you've given 20 URLs to the same hostname and --batch-per-host is set to 5, then the VU will make 5 requests right away in parallel and queue the rest, executing them as soon as a previous request is done and a slot opens. This will not run more request in parallel then the value of batch. Available in both the k6 run and the k6 cloud commands

1export let options = {
2  batchPerHost: 5,
3};

Blacklist IPs

Blacklist IP ranges from being called. Available in k6 run and k6 cloud commands.

1export let options = {
2  blacklistIPs: ['10.0.0.0/8'],
3};

Block Hostnames

New in v0.29.0

Blocks hostnames based on a list glob match strings. The pattern matching string can have a single * at the beginning such as *.example.com that will match anything before that such as test.example.com and test.test.example.com. Available in k6 run and k6 cloud commands.

1export let options = {
2  blockHostnames: ["test.k6.io" , "*.example.com"],
3};

$ k6 run --block-hostnames="test.k6.io,*.example.com" script.js

Compatibility Mode

Support running scripts with different ECMAScript compatibility modes.

Read about the different modes on the JavaScript Compatibility Mode documentation.

$ k6 run --compatibility-mode=base script.js

Config

Specify the config file in JSON format to read the options values. If the config file is not specified, k6 will look for config.json in the loadimpact/k6 directory inside the regular directory for configuration files on the operating system. Default config locations on different operating systems are:

Available in k6 run and k6 cloud commands:

An example of a config file is available here

⚠️ Keep in mind!

When running tests in k6 Cloud and using a non-default config.json file, you will have to specify the cloud token inside your config file in order to authenticate.

Discard Response Bodies

Specify if response bodies should be discarded by changing the default value of responseType to none for all HTTP requests. Highly recommended to be set to true and then only for the requests where the response body is needed for scripting to set responseType to text or binary. Lessens the amount of memory required and the amount of GC - reducing the load on the testing machine, and probably producing more reliable test results.

1export let options = {
2  discardResponseBodies: true,
3};

DNS

New in v0.29.0

This is a composite option that provides control of DNS resolution behavior with configuration for cache expiration (TTL), IP selection strategy and IP version preference. The TTL field in the DNS record is currently not read by k6, so the ttl option allows manual control over this behavior, albeit as a fixed value for the duration of the test run.

Note that DNS resolution is done only on new HTTP connections, and by default k6 will try to reuse connections if HTTP keep-alive is supported. To force a certain DNS behavior consider enabling the noConnectionReuse option in your tests.

Possible ttl values are:

• 0: no caching at all - each request will trigger a new DNS lookup.
• inf: cache any resolved IPs for the duration of the test run.
• any time duration like 60s, 5m30s, 10m, 2h, etc.; if no unit is specified (e.g. ttl=3000), k6 assumes milliseconds.

Possible select values are:

• first: always pick the first resolved IP.
• random: pick a random IP for every new connection.
• roundRobin: iterate sequentially over the resolved IPs.

Possible policy values are:

• preferIPv4: use IPv4 addresses if available, otherwise fall back to IPv6.
• preferIPv6: use IPv6 addresses if available, otherwise fall back to IPv4.
• onlyIPv4: only use IPv4 addresses, ignore any IPv6 ones.
• onlyIPv6: only use IPv6 addresses, ignore any IPv4 ones.
• any: no preference, use all addresses.

Here are some configuration examples:

k6 run --dns "ttl=inf,select=first,policy=any" script.js # the old k6 behavior before v0.29.0
K6_DNS="ttl=5m,select=random,policy=preferIPv4" k6 cloud script.js # new default behavior from v0.29.0

1export let options = {
2  dns: {
3    ttl: '1m',
4    select: 'roundRobin',
5    policy: 'any'
6  }
7}

Duration

A string specifying the total duration a test run should be run for. During this time each VU will execute the script in a loop. Available in k6 run and k6 cloud commands.

Together with the vus option, duration is a shortcut for a single scenario with a constant VUs executor.

1export let options = {
2  vus: 100,
3  duration: '3m',
4};

Extension Options

An object used to set configuration options for third-party collectors, like plugins.

This is an example of how to specify the test name (test runs/executions with the same name will be logically grouped for trending and comparison) when streaming results to k6 Cloud Performance Insights.

1export let options = {
2  ext: {
3    loadimpact: {
4      name: 'My test name',
5    },
6  },
7};

Execution Segment

New in v0.27.0

These options specify how to partition the test run and which segment to run. If defined, k6 will scale the number of VUs and iterations to be run for that segment, which is useful in distributed execution. Available in k6 run and k6 cloud commands.

For example, to run 25% of a test, you would specify --execution-segment '25%', which would be equivalent to --execution-segment '0:1/4', i.e. run the first 1/4 of the test. To ensure that each instance executes a specific segment, also specify the full segment sequence, e.g. --execution-segment-sequence '0,1/4,1/2,1'. This way one instance could run with --execution-segment '0:1/4', another with --execution-segment '1/4:1/2', etc. and there would be no overlap between them.

In v0.27.0 this distinction is not very important, but it will be required in future versions when support for test data partitioning is added.

Hosts

An object with overrides to DNS resolution, similar to what you can do with /etc/hosts on Linux/Unix or C:\\Windows\\System32\\drivers\\etc\\hosts on Windows. For instance, you could set up an override which routes all requests for test.k6.io to 1.2.3.4.

From v0.28.0 it is also supported to redirect only from certain ports and/or to certain ports.

⚠️ Keep in mind!

This does not modify the actual HTTP Host header, but rather where it will be routed.

1export let options = {
2  hosts: {
3    'test.k6.io': '1.2.3.4',
4    'test.k6.io:443': '1.2.3.4:8443',
5  },
6};

With the above code any request made to test.k6.io will be redirected to 1.2.3.4 without changing it port unless it's port is 443 which will be redirected to port 8443.

HTTP Debug

Log all HTTP requests and responses. Excludes body by default, to include body use --http-debug=full. Available in k6 run and k6 cloud commands.

Read more here.

1export let options = {
2  httpDebug: 'full',
3};

Include System Env Vars

Pass the real system environment variables to the runtime. Available in k6 run and k6 cloud commands.

1$ k6 run --include-system-env-vars ~/script.js

Insecure Skip TLS Verify

A boolean, true or false. When this option is enabled (set to true), all of the verifications that would otherwise be done to establish trust in a server provided TLS certificate will be ignored. This only applies to connections created by VU code, such as http requests. Available in k6 run and k6 cloud commands

1export let options = {
2  insecureSkipTLSVerify: true,
3};

Iterations

An integer value, specifying the total number of iterations of the default function to execute in the test run, as opposed to specifying a duration of time during which the script would run in a loop. Available both in the k6 run and k6 cloud commands.

Together with the vus option, iterations is a shortcut for a single scenario with a shared iterations executor.

By default, the maximum duration of a shared-iterations scenario is 10 minutes. You can adjust that time via the maxDuration option of the scenario, or by also specifying the duration global shortcut option.

Note that iterations aren't fairly distributed with this option, and a VU that executes faster will complete more iterations than others. Each VU will try to complete as many iterations as possible, "stealing" them from the total number of iterations for the test. So, depending on iteration times, some VUs may complete more iterations than others. If you want guarantees that every VU will complete a specific, fixed number of iterations, use the per-VU iterations executor.

1export let options = {
2  vus: 5,
3  iterations: 10,
4};

Or, to run 10 VUs 10 times each:

1export let options = {
2  vus: 10,
3  iterations: 100,
4};

Linger

A boolean, true or false, specifying whether the k6 process should linger around after test run completion. Available in the k6 run command.

1export let options = {
2  linger: true,
3};

Local IPs

A list of IPs, IP ranges and CIDRs from which VUs will make requests. The IPs will be sequentially given out to VUs. This option doesn't change anything on the OS level so the IPs need to be already configured on the OS level in order for k6 to be able to use them. Also IPv4 CIDRs with more than 2 IPs don't include the first and last IP as they are reserved for referring to the network itself and the broadcast address respectively.

This option can be used for splitting the network traffic from k6 between multiple network cards, thus potentially increasing the available network throughput. For example, if you have 2 NICs, you can run k6 with --local-ips="<IP-from-first-NIC>,<IP-from-second-NIC>" to balance the traffic equally between them - half of the VUs will use the first IP and the other half will use the second. This can scale to any number of NICs, and you can repeat some local IPs to give them more traffic. For example, --local-ips="<IP1>,<IP2>,<IP3>,<IP3>" will split VUs between 3 different source IPs in a 25%:25%:50% ratio.

Available in the k6 run command.

$ k6 run --local-ips=192.168.20.12-192.168.20-15,192.168.10.0/27 script.js

Log output

This option specifies where to send logs to and another configuration connected to it. Available in the k6 run command.

Possible values are:

• none - disable
• stdout - send to the standard output
• stderr - send to the standard error output (this is the default)
• loki - send logs to a loki server

The loki can additionally be configured as follows: loki=http://127.0.0.1:3100/loki/api/v1/push,label.something=else,label.foo=bar,limit=32,level=info,pushPeriod=5m32s,msgMaxSize=1231 Where all but the url in the beginning are not required. The possible keys with their meanings and default values:

1$ k6 run --log-output=stdout script.js

LogFormat

A value specifying the log format. By default, k6 includes extra debug information like date and log level. The other options available are:

• json: print all the debug information in JSON format.

• raw: print only the log message.

1$ k6 run --logformat raw test.js

Max Redirects

The maximum number of HTTP redirects that k6 will follow before giving up on a request and erroring out. Available in both the k6 run and the k6 cloud commands.

1export let options = {
2  maxRedirects: 10,
3};

Minimum Iteration Duration

Specifies the minimum duration for every single execution (i.e. iteration) of the default function should be. Any iterations that are shorter than it will cause that VU to sleep for the remainder of the time until the specified minimum duration is reached.

1export let options = {
2  minIterationDuration: '10s',
3};

No Connection Reuse

A boolean, true or false, specifying whether k6 should disable keep-alive connections. Available in k6 run and k6 cloud commands.

1export let options = {
2  noConnectionReuse: true,
3};

No Cookies Reset

This disables the default behavior of resetting the cookie jar after each VU iteration. If it's enabled, saved cookies will be persisted across VU iterations.

1export let options = {
2  noCookiesReset: true,
3};

No Summary

Disables end-of-test summary generation. Since k6 v0.30.0, that includes disabling the calling of handleSummary() and --summary-export. Available in the k6 run command.

1$ k6 run --no-summary ~/script.js

No Thresholds

Disables threshold execution. Available in the k6 run command.

1$ k6 run --no-thresholds ~/script.js

No Usage Report

A boolean, true or false. By default, k6 sends a usage report each time it is run, so that we can track how often people use it. If this option is set to true, no usage report will be made. To learn more, have a look at the Usage reports documentation. Available in k6 run commands.

1export let options = {
2  noUsageReport: true,
3};

No VU Connection Reuse

A boolean, true or false, specifying whether k6 should reuse TCP connections between iterations of a VU. Available in k6 run and k6 cloud commands.

1export let options = {
2  noVUConnectionReuse: true,
3};

Paused

A boolean, true or false, specifying whether the test should start in a paused state. To resume a paused state you'd use the k6 resume command. Available in k6 run and k6 cloud commands.

1export let options = {
2  paused: true,
3};

Results Output

Specify the results output. Please go to Results output for more information on all built-in output modules available and how to configure them. Since version 0.21, this option can be specified multiple times. Available in k6 run command.

1$ k6 run --out influxdb=http://localhost:8086/k6 script.js

RPS

The maximum number of requests to make per second, in total across all VUs. Available in k6 run and k6 cloud commands.

⚠️ Keep in mind!

This option has some caveats and is difficult to use correctly, so its usage is somewhat discouraged. For example, in the cloud/distributed execution, this option affects every k6 instance independently, i.e. it is not sharded like VUs are. We strongly recommend the use of arrival-rate executors to simulate constant RPS instead of this option.

1export let options = {
2  rps: 500,
3};

Considerations when running in the cloud

The option is set per load generator which means that the value you set in the options object of your test script will be multiplied by the number of load generators your test run is using. At the moment we are hosting 300 VUs per load generator instance. In practice that means that if you set the option for 100 rps, and run a test with 1000 VUs, you will spin up 4 load gen instances and effective rps limit of your test run will be 400

Scenarios

Define one or more execution patterns, with various VU and iteration scheduling settings, running different exported functions (besides default!), using different environment variables, tags, and more.

See the Scenarios article for details and more examples.

Available in k6 run and k6 cloud commands.

1export let options = {
2  scenarios: {
3    my_api_scenario: {
4      // arbitrary scenario name
5      executor: 'ramping-vus',
6      startVUs: 0,
7      stages: [
8        { duration: '5s', target: 100 },
9        { duration: '5s', target: 0 },
10      ],
11      gracefulRampDown: '10s',
12      env: { MYVAR: 'example' },
13      tags: { my_tag: 'example' },
14    },
15  },
16};

Setup Timeout

Specify how long the setup() function is allow to run before it's terminated and the test fails.

1export let options = {
2  setupTimeout: '30s',
3};

Stages

A list of VU { target: ..., duration: ... } objects that specify the target number of VUs to ramp up or down to for a specific period. Available in k6 run and k6 cloud commands.

It is a shortcut option for a single scenario with a ramping VUs executor. If used together with the VUs option, the vus value is used as the startVUs option of the executor.

1// The following config would have k6 ramping up from 1 to 10 VUs for 3 minutes,
2// then staying flat at 10 VUs for 5 minutes, then ramping up from 10 to 35 VUs
3// over the next 10 minutes before finally ramping down to 0 VUs for another
4// 3 minutes.
5
6export let options = {
7  stages: [
8    { duration: '3m', target: 10 },
9    { duration: '5m', target: 10 },
10    { duration: '10m', target: 35 },
11    { duration: '3m', target: 0 },
12  ],
13};

Summary export

New in v0.26.0

Save the end-of-test summary report to a JSON file that includes data for all test metrics, checks and thresholds. This is useful to get the aggregated test results in a machine-readable format, for integration with dashboards, external alerts, CI pipelines, etc.

Starting with k6 v0.30.0, while this feature is not deprecated yet, its usage is discouraged, see the explanation why here. For a better and more flexible JSON export, as well as export of the summary data to different formats (e.g. JUnit/XUnit/etc. XML, HTML, .txt) and complete summary customization, see the new handleSummary() callback.

Available in the k6 run command.

1$ k6 run --summary-export export.json ~/script.js
2
3# or...
4
5$ K6_SUMMARY_EXPORT="export.json" k6 run ~/script.js

See an example file on the Results Output page.

Supply environment variables

Add/override an environment variable with VAR=value. Available in k6 run and k6 cloud commands.

To make the system environment variables available in the k6 script via __ENV, use the --include-system-env-vars option.

1$ k6 run -e FOO=bar ~/script.js

System Tags

Specify which System Tags will be in the collected metrics. Some collectors like the cloud one may require that certain system tags be used. You can specify the tags as an array from the JS scripts or as a comma-separated list via the CLI. Available in k6 run and k6 cloud commands

1export let options = {
2  systemTags: ['status', 'method', 'url'],
3};

Summary Time Unit

Define which time unit will be used for all time values in the end-of-test summary. Possible values are s (seconds), ms (milliseconds) and us (microseconds). If no value is specified, k6 will use mixed time units, choosing the most appropriate unit for each value.

1export let options = {
2  summaryTimeUnit: 'ms',
3};

Summary Trend Stats

Define which stats for Trend metrics (e.g. response times, group/iteration durations, etc.) will be shown in the end-of-test summary. Possible values include avg (average), med (median), min, max, count (since k6 v0.26.0), as well as arbitrary percentile values (e.g. p(95), p(99), p(99.99), etc.).

For further summary customization and exporting the summary in various formats (e.g. JSON, JUnit/XUnit/etc. XML, HTML, .txt, etc.), see the new handleSummary() callback introduced in k6 v0.30.0.

1export let options = {
2  summaryTrendStats: ['avg', 'min', 'med', 'max', 'p(95)', 'p(99)', 'p(99.99)', 'count'],
3};

1$ k6 run --summary-trend-stats="avg,min,med,max,p(90),p(99.9),p(99.99),count" ./script.js

Tags

Specify tags that should be set test wide across all metrics. If a tag with the same name has been specified on a request, check or custom metrics it will have precedence over a test wide tag. Available in k6 run and k6 cloud commands.

1export let options = {
2  tags: {
3    name: 'value',
4  },
5};

Teardown Timeout

Specify how long the teardown() function is allowed to run before it's terminated and the test fails.

1export let options = {
2  teardownTimeout: '30s',
3};

Thresholds

A collection of threshold specifications to configure under what condition(s) a test is considered successful or not, when it has passed or failed, based on metric data. To learn more, have a look at the Thresholds documentation. Available in k6 run commands.

1export let options = {
2  thresholds: {
3    http_req_duration: ['avg<100', 'p(95)<200'],
4    'http_req_connecting{cdnAsset:true}': ['p(95)<100'],
5  },
6};

Throw

A boolean, true or false, specifying whether to throw errors on failed HTTP requests or not. Available in k6 run and k6 cloud commands.

1export let options = {
2  throw: true,
3};

TLS Auth

A list of TLS client certificate configuration objects. Each object needs to specify for which host(s)/domain(s) the given client certificate is valid for.

1export let options = {
2  tlsAuth: [
3    {
4      domains: ['example.com'],
5      cert: open('mycert.pem'),
6      key: open('mycert-key.pem'),
7    },
8  ],
9};

TLS Cipher Suites

A list of cipher suites allowed to be used by in SSL/TLS interactions with a server. For a full listing of available ciphers go here.

1export let options = {
2  tlsCipherSuites: [
3    'TLS_RSA_WITH_RC4_128_SHA',
4    'TLS_RSA_WITH_AES_128_GCM_SHA256',
5  ],
6};

TLS Version

Either a string representing the only SSL/TLS version allowed to be used in interactions with a server, or an object specifying the "min" and "max" versions allowed to be used.

1export let options = {
2  tlsVersion: 'tls1.2',
3};
4
5// or...
6
7export let options = {
8  tlsVersion: {
9    min: 'ssl3.0',
10    max: 'tls1.2',
11  },
12};

User Agent

A string specifying the user-agent string to use in User-Agent headers when sending HTTP requests. Setting it to an empty string will not send a User-Agent header since v0.29.0. Available in k6 run and k6 cloud commands

1export let options = {
2  userAgent: 'MyK6UserAgentString/1.0',
3};

VUs

An integer value specifying the number of VUs to run concurrently, used together with the iterations or duration options. If you'd like more control look at the stages option or scenarios.

Available in k6 run and k6 cloud commands.

1export let options = {
2  vus: 10,
3  duration: '1h',
4};

VUs Max

⚠️ Keep in mind!

This option was deprecated in k6 version 0.27.0. See scenarios and the externally controlled executor instead.