CobaltPDF 1.1.0

CobaltPDF

CobaltPDF is a high-performance .NET 8 library that converts HTML pages and strings into pixel-perfect PDFs using a managed Chromium browser pool.

Features

• 🚀 Browser pooling — Chromium instances kept warm between requests; no per-request startup cost
• ✍️ Fluent API — chain options naturally: renderer.Landscape().AddCookie(…).RenderUrlAsPdfAsync(…)
• ⏳ Wait strategies — network idle, fixed delay, CSS selector, JavaScript expression, or manual signal
• 🍪 Cookie & storage injection — set cookies, localStorage, and sessionStorage before navigation
• 🖋️ Custom JavaScript — execute arbitrary JS before capture; use window.cobaltNotifyRender() for precise control
• 🔤 Fonts — point to a local directory and any .ttf, .otf, .woff, .woff2 file is injected automatically
• 📄 Headers, footers & watermarks — full HTML templates with pageNumber/totalPages tokens
• 🔒 Encryption — user + owner passwords with print/copy/modify permissions
• 📋 Metadata — title, author, subject, keywords, creator embedded in the PDF
• 🔄 Lazy loading — scroll N viewport-heights before capture to trigger infinite-scroll content
• 💉 DI support — services.AddCobaltPdf(…) for ASP.NET Core / generic host
• ☁️ Cloud-ready — built-in presets for Linux, Docker, Azure, and AWS
• 📡 Microservice-ready — companion CobaltPDF.Requests package lets clients send JSON payloads without installing Chromium

Quick Start

dotnet add package CobaltPDF

using CobaltPdf;
using CobaltPdf.Configuration;

// One-time setup at application startup
CobaltEngine.Configure(options =>
{
    options.MinSize = 2;
    options.MaxSize = Environment.ProcessorCount;
});
// On Linux, --no-sandbox, --disable-gpu, and --disable-dev-shm-usage are added automatically.
// Or use a cloud preset: CobaltEngine.Configure(CloudEnvironment.ConfigureForDocker);

// Render a URL to PDF
var renderer = new CobaltEngine();
var pdf = await renderer.RenderUrlAsPdfAsync("https://example.com");
pdf.SaveAs("output.pdf");

// Render an HTML string
var pdf2 = await renderer.RenderHtmlAsPdfAsync("<h1>Hello, World!</h1>");
Console.WriteLine($"{pdf2.Length} bytes");

Cloud Deployments

Use the built-in CloudEnvironment presets instead of configuring flags manually:

// Docker
CobaltEngine.Configure(CloudEnvironment.ConfigureForDocker);

// Azure Functions Premium Plan
CobaltEngine.Configure(CloudEnvironment.ConfigureForAzure);

// AWS ECS / Fargate
CobaltEngine.Configure(CloudEnvironment.ConfigureForAwsEcs);

// Memory-constrained (AWS Lambda custom runtime, small containers)
CobaltEngine.Configure(CloudEnvironment.ConfigureForLowMemory);

See the Deployment guide for full platform walkthroughs.

Fluent API

var pdf = await new CobaltEngine()
    .Landscape()
    .WithPaperFormat("A3")
    .EmulateMediaType(CssMediaType.Print)
    .WithHeader("<div style='text-align:center;width:100%'>My Report</div>")
    .WithFooter("<div style='text-align:center;width:100%'>Page <span class='pageNumber'></span></div>")
    .AddCookie("session", "abc123", "example.com")
    .WaitFor(WaitOptions.NetworkIdle)
    .RenderUrlAsPdfAsync("https://example.com/report");

pdf.SaveAs("report.pdf");

ASP.NET Core Integration

// Program.cs
builder.Services.AddCobaltPdf(o =>
{
    CloudEnvironment.ConfigureForDocker(o);
    o.MaxSize = 4;
});

// Controller / service
public class ReportService(CobaltEngine renderer)
{
    public async Task<byte[]> GenerateAsync(string url)
        => (await renderer.RenderUrlAsPdfAsync(url)).BinaryData;
}

Microservice / Azure Function Pattern

When deploying CobaltPDF as a dedicated PDF rendering service, use the companion CobaltPDF.Requests package in your client application. It contains only the serialisable request and response models — no Chromium, no Playwright.

[Web App]  ──── CobaltPDF.Requests (tiny, ~50 KB) ────▶ HTTP POST ──▶ [Azure Function]
                PdfRequest / PdfResponse                               CobaltPDF (full)

Client (web app):

dotnet add package CobaltPDF.Requests

var request = new PdfRequest
{
    Url         = "https://myapp.com/invoice/42",
    Landscape   = true,
    PaperFormat = "A4",
    Metadata    = new() { Title = "Invoice #42" },
    Encryption  = new() { UserPassword = "open123" }
};

var response = await httpClient.PostAsJsonAsync("/api/pdf", request);
var pdfBytes = (await response.Content.ReadFromJsonAsync<PdfResponse>())!.ToBytes();

Azure Function (rendering service):

dotnet add package CobaltPDF   # CobaltPDF.Requests is included automatically

[Function("GeneratePdf")]
public async Task<HttpResponseData> Run(
    [HttpTrigger(AuthorizationLevel.Function, "post")] HttpRequestData req,
    CancellationToken ct)
{
    var request = await req.ReadFromJsonAsync<PdfRequest>();
    var pdf = await request!.ExecuteAsync(_renderer, ct);

    var response = req.CreateResponse(HttpStatusCode.OK);
    response.Headers.Add("Content-Type", "application/pdf");
    await response.Body.WriteAsync(pdf.BinaryData, ct);
    return response;
}

See the HTTP Requests guide for the full JSON schema and more examples.

Requirements

Chromium is bundled as a NuGet dependency — no separate installation required.

Documentation

Full documentation is available at cobaltpdf.com/docs.

License

CobaltPDF is a commercial product. A license key is required for production use. A trial watermark is applied to all PDFs generated without a valid license.

CobaltEngine.SetLicense("YOUR-LICENSE-KEY");

View licensing options →

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