Ruby · Code recipe
Run a Lighthouse audit in Ruby
Score any page for performance, accessibility, best practices and SEO, in Ruby 3.1+ with Net::HTTP from the standard library. Every program on this page runs as it stands — each one was run against a stub of the API before it was published.
By Roger Campos · Last updated: September 2026
TL;DR
To run a Lighthouse audit in Ruby, POST a URL and a device to https://urlpipe.dev/lighthouse and read the JSON with JSON.parse: four category scores from 0 to 1 and the lab metrics, LCP, CLS and TBT among them. An audit takes around 15 seconds, so the async variant with a webhook suits production. It costs 2 credits.
Free plan, no credit card. 1,000 credits a month.
One POST to /lighthouse runs a real Lighthouse audit in Chrome and answers with the four category scores — performance, accessibility, best practices, SEO — and the lab metrics behind the performance score. device picks mobile (the default, throttled CPU and network) or desktop.
In Ruby the report is read with JSON.parse. Scores run from 0 to 1, so the program multiplies by 100 to print what the Lighthouse report shows; metrics carry a ready-formatted displayValue. The guide to reading a Lighthouse audit explains what each number means.
Setup
Before you start
Nothing to install: net/http and json are part of Ruby. Put your API key in the environment so it never lands in the file.
ruby --version # 3.1 or later
export URLPIPE_API_KEY="your_api_key"
The request
Print the four scores, LCP, CLS and TBT
sync: true keeps the request open until the result is ready. use_ssl: has to be asked for — Net::HTTP does not infer it from the scheme — and abort prints to stderr and exits 1. dig walks the nested keys and returns nil for a category or metric Lighthouse could not compute.
require "json"
require "net/http"
uri = URI("https://urlpipe.dev/lighthouse")
# read_timeout: a sync call can take up to 60 s, Net::HTTP's default.
res = Net::HTTP.start(uri.host, uri.port, use_ssl: uri.scheme == "https", read_timeout: 90) do |http|
http.post(uri.path, { url: "https://example.com", device: "mobile", sync: true }.to_json,
"Authorization" => "Bearer #{ENV.fetch("URLPIPE_API_KEY")}",
"Content-Type" => "application/json")
end
abort "URLpipe answered #{res.code}: #{res.body}" unless res.is_a?(Net::HTTPOK)
report = JSON.parse(res.body)
%w[performance accessibility best-practices seo].each do |name|
score = report.dig("categories", name, "score")
puts "#{name}: #{score ? (score * 100).round : "n/a"}"
end
{
"LCP" => "largest-contentful-paint",
"CLS" => "cumulative-layout-shift",
"TBT" => "total-blocking-time"
}.each do |label, key|
puts "#{label}: #{report.dig("metrics", key, "displayValue") || "n/a"}"
end
Run it: ruby lighthouse_audit.rb
Given the example response on the docs page, it prints:
performance: 95
accessibility: 88
best-practices: 92
seo: 90
LCP: 2.5 s
CLS: 0.05
TBT: 150 msAsync
The async variant: a token, a webhook and a poll
Leave out sync and the answer is a token, straight away. Net::HTTP reports the status as a string, so the poll compares res.code with "202", not the number.
require "json"
require "net/http"
API = URI("https://urlpipe.dev")
def send_request(request)
request["Authorization"] = "Bearer #{ENV.fetch("URLPIPE_API_KEY")}"
Net::HTTP.start(API.host, API.port, use_ssl: API.scheme == "https") { |http| http.request(request) }
end
# No sync: the request is accepted at once and the work carries on without you.
post = Net::HTTP::Post.new(URI.join(API, "/lighthouse"), "Content-Type" => "application/json")
post.body = {
url: "https://example.com",
device: "mobile",
report_to: "https://your-app.com/webhooks/urlpipe",
labels: { customer: "acme" }
}.to_json
res = send_request(post)
abort "URLpipe answered #{res.code}: #{res.body}" unless res.is_a?(Net::HTTPOK)
token = JSON.parse(res.body).fetch("token")
puts "Accepted #{token}"
# The result is POSTed to report_to when it is ready. Polling by token is the
# other way to collect it: no endpoint needed, and a backup for the webhook.
60.times do
res = send_request(Net::HTTP::Get.new(URI.join(API, "/result/#{token}")))
break unless res.code == "202" # 202 means still processing
sleep 2
end
case res.code
when "200" then nil
when "202" then abort "Still processing after two minutes; try the token again later."
when "422" then abort "The analysis failed: #{JSON.parse(res.body)["error"]}"
when "410" then abort "The result is past the 30-day window; send the request again."
else abort "URLpipe answered #{res.code}: #{res.body}"
end
report = JSON.parse(res.body)
%w[performance accessibility best-practices seo].each do |name|
score = report.dig("categories", name, "score")
puts "#{name}: #{score ? (score * 100).round : "n/a"}"
end
{
"LCP" => "largest-contentful-paint",
"CLS" => "cumulative-layout-shift",
"TBT" => "total-blocking-time"
}.each do |label, key|
puts "#{label}: #{report.dig("metrics", key, "displayValue") || "n/a"}"
end
Run it: ruby lighthouse_audit_async.rb
Errors
Handle errors and retries
Pattern matching on [status, code] keeps the retry rules in one place. A 401 answers in plain text, so it is checked before JSON.parse, and a body that still is not JSON becomes an empty hash.
require "json"
require "net/http"
class URLpipeError < StandardError; end
# POST a sync request and return the response, or raise URLpipeError.
def urlpipe(path, payload, attempts: 5)
uri = URI("https://urlpipe.dev#{path}")
attempts.times do |attempt|
res = Net::HTTP.start(uri.host, uri.port, use_ssl: uri.scheme == "https", read_timeout: 90) do |http|
http.post(uri.path, payload.merge(sync: true).to_json,
"Authorization" => "Bearer #{ENV.fetch("URLPIPE_API_KEY")}",
"Content-Type" => "application/json")
end
return res if res.code == "200"
raise URLpipeError, "401: the API key is missing or wrong. Check URLPIPE_API_KEY." if res.code == "401"
body = begin
JSON.parse(res.body)
rescue JSON::ParserError
{}
end
code = body["error"].to_s
detail = body["message"] ? "#{code}: #{body["message"]}" : code
case [ res.code, code ]
in [ "429", "rate_limited" ]
# Sending too fast: Retry-After says how long the window has left.
sleep Integer(res["Retry-After"] || 1)
in [ "429", "concurrency_limit" ]
# Every parallel slot on your plan is busy with your own requests.
sleep 2**attempt
in [ "504", _ ]
# Still running on our side; the token collects it from GET /result/:token.
raise URLpipeError, "504 processing_timeout: collect it later with token #{body["token"]}"
else
# 403 email_unverified, 422 (a bad parameter, or a page that would not load),
# 429 quota_exceeded: sending the same request again gets the same answer.
raise URLpipeError, "#{res.code}: #{detail}"
end
end
raise URLpipeError, "429: still refused after #{attempts} attempts"
end
begin
res = urlpipe("/lighthouse", { url: "https://example.com", device: "mobile" })
rescue URLpipeError => e
abort "URLpipe: #{e.message}"
end
report = JSON.parse(res.body)
%w[performance accessibility best-practices seo].each do |name|
score = report.dig("categories", name, "score")
puts "#{name}: #{score ? (score * 100).round : "n/a"}"
end
{
"LCP" => "largest-contentful-paint",
"CLS" => "cumulative-layout-shift",
"TBT" => "total-blocking-time"
}.each do |label, key|
puts "#{label}: #{report.dig("metrics", key, "displayValue") || "n/a"}"
end
Run it: ruby lighthouse_audit_errors.rb
Details
What to know about /lighthouse
- Lighthouse 13 reports four categories; the
pwakey is alwaysnull, kept so the shape does not change. - The performance score weights TBT 30%, LCP 25%, CLS 25%, FCP 10% and Speed Index 10%.
- INP needs real users and cannot be measured in a lab run; TBT is its lab stand-in.
"include_audits": "true"adds the full list of audits, with the elements to fix. Mobile and desktop are cached separately.- Want the audit run on a schedule, with a history and alerts? Full Stack Audit sells that as a monitored report; URLpipe is the primitive underneath.
Client library
Or use the official Ruby client
The same call in one line, with retries that never bill twice, typed errors, long analyses waited out for you and webhook verification. Ruby 3.1+, no dependencies.
# gem install urlpipe
require "urlpipe"
client = Urlpipe::Client.new # reads ENV["URLPIPE_API_KEY"]
page = client.markdown("https://example.com")
puts page.dataFAQ
Frequently asked questions
Mobile or desktop — which device should I audit?
Why isn't INP in the results?
Why use the async variant for Lighthouse?
Do I need an SDK to call URLpipe from Ruby?
Get a key and run it.
Free plan, no card. Paste your key into URLPIPE_API_KEY and every program on this page runs as it is.