📄 Bidi2pdfRails

Bidi2pdfRails is the official Rails integration for Bidi2pdf — a modern, headless-browser-based PDF rendering engine.
Generate high-fidelity PDFs directly from your Rails views or external URLs with minimal setup.

• 🔍 Accurate PDF rendering using a real browser engine
• 💾 Supports both HTML string rendering and remote URL conversion
• 🔐 Built-in support for authentication (Basic Auth, cookies, headers)
• 🧰 Full test suite with examples for Rails controller integration
• 🧠 Sensible defaults, yet fully configurable

Add to your Gemfile:

gem "bidi2pdf-rails"
# for development only
# gem "bidi2pdf-rails", github: "dieter-medium/bidi2pdf-rails", branch: "main"

# Optional for performance:
# gem "websocket-native"

Install it:

bundle install

Generate the config initializer:

bin/rails generate bidi2pdf_rails:initializer

%%{  init: {
      "theme": "base",
      "themeVariables": {
        "primaryColor":  "#E0E7FF",
        "secondaryColor":"#FEF9C3",
        "tertiaryColor": "#DCFCE7",
        "edgeLabelBackground":"#FFFFFF",
        "fontSize":"14px",
        "nodeBorderRadius":"6"
      }
    }
}%%
flowchart LR
%% ───────────────────────────────────
%% Rails world
    subgraph R["fa:fa-rails Rails World"]
        direction TB
        R1["fa:fa-gem Your Rails App"]
        R2["fa:fa-plug bidi2pdf-rails Engine"]
        R3["fa:fa-cog&nbsp;ActionController::Renderers<br/><code>render pdf:</code>"]
        R4["fa:fa-file-code Rails&nbsp;View&nbsp;(ERB/Haml)"]
    end

%% bidi2pdf core
    subgraph B["fa:fa-gem bidi2pdf Core"]
        direction TB
        B1["fa:fa-gem bidi2pdf"]
    end

%% Chrome env
    subgraph C["fa:fa-chrome Chrome Environment"]
        direction LR
        C1["fa:fa-chrome Local&nbsp;Chrome<br/>(sub-process)"]
        C2["fa:fa-docker Docker&nbsp;Chrome<br/>(remote)"]
    end

%% Artifact
    P[[PDF&nbsp;File]]

%% ─── Flows ─────────────────────────
R1 -- " Controller&nbsp;invokes<br/><code>render pdf:</code> " --> R3
R3 -- " HTML&nbsp;+&nbsp;Assets<br/>(via&nbsp;<code>render_to_string</code>) " --> R2
R2 -- " HTML&nbsp;/&nbsp;URL&nbsp;+&nbsp;CSS/JS " --> B1
B1 -- " WebDriver&nbsp;BiDi " --> C1
B1 -- " WebDriver&nbsp;BiDi " --> C2
C1 -- " PDF&nbsp;bytes " --> B1
C2 -- " PDF&nbsp;bytes " --> B1
B1 -- " PDF&nbsp;stream " --> R2
R2 -- " send_data " --> R1
R1 -- " Download/inline " --> P

%% ─── Styling classes ───────────────
classDef rails fill: #E0E7FF, stroke: #6366F1, color: #1E1B4B
classDef engine fill: #c7d2fe, stroke: #4338CA, color: #1E1B4B
classDef bidi fill: #E0E7FF, stroke: #4f46e5, color: #1E1B4B
classDef chrome fill: #FEF9C3, stroke: #F59E0B, color: #78350F
classDef artifact fill: #DCFCE7, stroke: #16A34A, color: #065F46

class R1 rails
class R2 engine
class R3,R4 rails
class B1 bidi
class C1,C2 chrome
class P artifact

# app/controllers/invoices_controller.rb

def show
  render pdf: "invoice",
         template: "invoices/show",
         layout: "pdf",
         locals: { invoice: @invoice },
         print_options: { landscape: true },
         wait_for_network_idle: true
end

def convert
  render pdf: "external-report",
         url: "https://example.com/dashboard",
         wait_for_page_loaded: false,
         print_options: { page: { format: :A4 } }
end

Need to convert pages that require authentication? No problem. Use:

• auth: { username:, password: }
• cookies: { session_key: value }
• headers: { "Authorization" => "Bearer ..." }

Example:

render pdf: "secure",
       url: secure_report_url,
       auth: { username: "admin", password: "secret" }

Or use global config in bidi2pdf_rails.rb initializer:

config.render_remote_settings.basic_auth_user = ->(_) { "admin" }
config.render_remote_settings.basic_auth_pass = ->(_) { Rails.application.credentials.dig(:pdf, :auth_pass) }

When rendering HTML with render_to_string, Chromium needs access to your assets (CSS, images, fonts).
Enable CORS for /assets using rack-cors:

# Gemfile
gem 'rack-cors'

# config/initializers/cors.rb
Rails.application.config.middleware.insert_before 0, Rack::Cors do
  allow do
    origins '*'
    resource '/assets/*', headers: :any, methods: [:get, :options]
  end
end

Deadlock Warning
In Rails development mode, loopback asset or page requests (e.g., when ChromeDriver or Grover fetches your own app’s URL) can deadlock under Rails’ autoload interlock. See Puma’s docs: https://puma.io/puma/file.rails_dev_mode.html

Workarounds:

1. Precompile & serve assets statically (in config/environments/development.rb):

   config.public_file_server.enabled = true

2. Run Puma with single-threaded workers:

   workers ENV.fetch("WEB_CONCURRENCY") { 2 }
   threads 1, 1

Implementing these steps helps avoid interlock-induced deadlocks when generating PDFs in development.

This repo includes real integration tests that serve as usage documentation:

• Download PDF with .pdf format
• Render protected remote URLs using Basic Auth, cookies, and headers
• Inject custom CSS into a Webpage before printing
• Inject custom JS into a Webpage before printing
• Using callbacks to modify the PDF before sending
• Using a remote chromedriver
• Using ActiveStorage and ActiveJob to generate PDFs in the background

Bidi2pdfRails is highly configurable.

See full config options in:

bin/rails generate bidi2pdf_rails:initializer

Or explore Bidi2pdfRails::Config::CONFIG_OPTIONS in the source.

On top of Bidi2pdf test helpers, Bidi2pdfRails provides a suite of RSpec helpers (activated with pdf: true) to simplify PDF-related testing:

– inside_container? → true if running in Docker
– environment_type → one of :ci, :codespaces, :container, :local
– environment_…? predicates for each type

– with_render_setting(key, value)
– with_pdf_settings(key, value)
– with_lifecycle_settings(key, value)
– with_chromedriver_settings(key, value)
– with_proxy_settings(key, value)
…plus automatic reset after each pdf: true example

– server_running?, server_port, server_host, server_url
– boots a Puma test server before suite type: :request, pdf: true specs
– shuts it down afterward

– get_pdf_response(path) → fetches raw HTTP response
– follow_redirects(response, max_redirects = 10)

Tag your examples or example groups:

RSpec.describe "Invoice PDF", type: :request, pdf: true do
  it "renders a complete PDF" do
    response = get_pdf_response "/invoices/123.pdf"
    expect(response['Content-Type']).to eq("application/pdf")
  end
end

Pull requests, issues, and ideas are all welcome 🙏
Want to contribute? Just fork, branch, and PR like a boss.

Contribution guide coming soon!

This gem is released under the MIT License.
Use freely — and responsibly.