CloudConvert and RelayPDF both turn HTML into PDF with Chrome or Chromium. CloudConvert is a general file converter: 212 formats across 11 categories on the public catalog, jobs built from import, convert, and export tasks, and a browser drop zone. RelayPDF is a PDF-first API: one POST /v1/pdf for HTML, public URL, Markdown, or a Handlebars template, plus convert, images, and a PDF tool set on the same key.
If you are evaluating a CloudConvert HTML to PDF API against a dedicated print pipeline, start with the table. CloudConvert wins on format breadth, storage connectors, and job graphs. RelayPDF wins on Chromium print CSS defaults, stored templates, MCP/CLI, and PDF tools. Neither page invents ratings.
Feature table
Public pages as of 23 August 2026. Yes means the vendor documents the capability.
| Capability | RelayPDF | CloudConvert |
|---|---|---|
| HTML to PDF | Yes. POST /v1/pdf, html as UTF-8 JSON (not Base64). Chromium. printBackground default true. | Yes. capture-website or convert HTML. Chrome. Homepage and /apis/html-to-pdf. |
| URL to PDF | Yes. Public http(s). extraHTTPHeaders and cookies on options. Private and loopback hosts rejected. | Yes. URL plus custom Authorization headers for protected resources. |
| Markdown / templates | GFM Markdown and published Handlebars (templateId + templateData) on /v1/pdf. | Not advertised as first-party Markdown or Handlebars templates. Convert the HTML you already have. |
| Format catalog | Office via LibreOffice on /v1/convert (PDF, DOCX, XLSX, HTML, PNG). wkhtmltopdf as a convert engine. | 212 formats, 11 categories: documents, images, video, audio, spreadsheets, slides, ebooks, archives, vector, CAD, fonts. |
| Screenshots | POST /v1/images. png, jpeg, webp. | Capture-website output_format image variants; plus image convert pairs. |
| Merge / PDF tools | merge 2-20, extract, AES-256 protect, stamp, rotate, compress, info, text (no OCR), AcroForm fill, barcodes, zip. Tool inputs 15 MB. | Job graph: convert, optimize, watermark, thumbnails. Not advertised as AcroForm fill. |
| Jobs / storage | response binary (default), url (24h), or async + callbackUrl. | Jobs of import/convert/export tasks. S3, Azure, Google Cloud. Sync host sync.api.cloudconvert.com. |
| MCP / CLI | First-party CLI (@relaypdf/cli) and stdio MCP. Contents not logged. | Official CLI and SDKs (PHP, Node, Python, Ruby, Java, .NET). Zapier, Power Automate, Make, n8n. No first-party MCP. |
| Billing | Prepaid wallet. $0.015 Chromium PDF or screenshot. $0.04 LibreOffice. $0.025 wkhtml. $0.005 tools. Failures not billed. Credit never expires. $5 signup, no card. | Credits: typically 1 credit per minute plus a base (General 1, Office→PDF 2, PDF→Office 4). Free 10/day. Packages never expire. Subscriptions monthly reset. HTML-to-PDF marketing: from $0.008/file at 10,000 files. |
What each product actually is
CloudConvert homepage: convert any file; 200+ formats (catalog: 212 / 11 categories). The API is jobs, not a single print route. You import (URL, upload, or object storage), convert or capture-website, then export (URL or storage). HTML-to-PDF marketing is explicit: latest Chrome, page size, margins, zoom, headers and footers, wait for a CSS selector, async webhooks or a synchronous API, and chained jobs (watermark, thumbnail). Regions: nearest, or eu-central / us-east. Sandbox API: unlimited jobs on a whitelist of files, no credits.
RelayPDF is a managed Chromium print API first. POST /v1/pdf takes exactly one of html, url, markdown, or templateId. Office and wkhtmltopdf go to POST /v1/convert. Tools are /v1/pdf/* plus barcodes and zip. One bearer key covers REST, official SDKs, CLI, and MCP. Binary is the default response.
Both products are honest about Chrome for HTML. CloudConvert is a conversion platform that also prints. RelayPDF is a print and PDF-tool platform that also converts Office.
Where CloudConvert wins
Format pairs. Audio, video, archives, CAD, RAW, ebooks, and fonts are first-class. RelayPDF convert is LibreOffice and wkhtmltopdf. If the pipeline is “whatever file lands in the bucket,” CloudConvert’s catalog is the product.
Job graph and storage. One job can import from S3, convert twice, watermark, and export back. RelayPDF is request-in, PDF-out, with optional 24-hour URL or async poll. You wire storage yourself.
Envelope. Free: 1 GB, 5 minutes, 5 concurrent tasks. Paid packages: unlimited file size and processing time (their table). RelayPDF Chromium timeout is 60 seconds; tool inputs 15 MB. Long media or multi-hundred-megabyte Office files match CloudConvert’s published envelope.
Auth on capture. CloudConvert documents custom Authorization headers on URL capture. RelayPDF documents extraHTTPHeaders and cookies, and still rejects private, loopback, and metadata hosts.
Compliance they publish. Enterprise column: 99.9% SLA, data processing agreement, SSO / SAML 2.0, custom contracts. Those are CloudConvert claims. This page does not attach them to RelayPDF.
Price at volume. Their HTML-to-PDF page quotes from $0.008 per file at 10,000 files/month. A short general conversion is one credit. RelayPDF Chromium PDF is $0.015 per success. CloudConvert can win on unit cost if the job stays in the General bucket and finishes inside a minute. Office→PDF is 2 credits; PDF→Office is 4.
Human UI. The site is a converter first. Developers use the Job Builder. RelayPDF is API-first.
Where RelayPDF wins
Chromium print CSS. formats letter, legal, tabloid, ledger, A0–A6; waitUntil load / domcontentloaded / networkidle0 / networkidle2 (default networkidle0); printBackground default true; preferCSSPageSize; header/footer placeholders pageNumber, totalPages, date, title; timeout max 60s. CloudConvert documents page size, margins, zoom, headers, footers, and wait-for-selector. It does not document that print stack as the default product surface.
Templates. Publish a Handlebars draft, then POST templateId + templateData. Same $0.015 as raw HTML. CloudConvert expects you to render HTML elsewhere.
PDF-first toolkit. Merge 2–20, extract, protect, unlock, stamp, rotate, delete pages, compress, info, text (not OCR), form fields, form fill, bookmarks, raster, from-images, barcodes, zip. CloudConvert jobs cover convert, optimize, watermark, and thumbnails. AcroForm fill is the RelayPDF cell.
MCP and CLI. `npx @relaypdf/cli` then `relaypdf pdf`, `convert`, `merge`, `mcp`. Stdio MCP for Cursor and Claude; keys stay in ~/.config/relaypdf. CloudConvert ships a CLI and SDKs. It does not ship first-party MCP.
Prepaid operations. Cents per successful call. Failures never debit. Credit never expires. Packs add 5–15 percent. CloudConvert meters credits × minutes × conversion class. Packages also never expire; subscriptions reset monthly.
Markdown on the print route. GFM in, PDF out. No extra convert task.
Engines, not brands
Chrome/Chromium is the right default for Flex, Grid, webfonts, and client-rendered pages. Both vendors use it for HTML to PDF.
CloudConvert also pins engines on convert tasks (example from their docs: office vs libreoffice, fixed engine version). That matters when you convert Office in both directions and need a stable layout.
RelayPDF defaults HTML to Chromium and keeps wkhtmltopdf on /v1/convert for old markup. LibreOffice is $0.04; wkhtmltopdf is $0.025. Compare real files. Do not assume Office→PDF looks identical across engines.
When to use which
Stay on CloudConvert when
- The job is many format pairs, not one print CSS document.
- You already chain import/convert/export into S3, Azure, or GCS.
- Files or runtimes exceed RelayPDF’s 60s Chromium budget or 15 MB tool cap.
- You need their published enterprise SLA, DPA, or SSO.
- Volume math at their credit rates beats $0.015 per PDF.
Move to RelayPDF when
- The workload is HTML, URL, Markdown, or Handlebars → PDF with Chromium print options and a binary response.
- You need AcroForm fill, stamp, merge, or the $0.005 tool set on the same key.
- Agents should call first-party MCP instead of wrapping a job graph.
- You want prepaid cents per successful document, not credit-minutes.
Do not rip out a working CloudConvert job on a Friday. Port one real HTML document and compare bytes and CSS.
Limits (both)
RelayPDF: public URLs only (private/loopback/metadata rejected), 60s Chromium timeout, 15 MB tool inputs, merge 2–20, rate limits on writes. /v1/pdf/text is not OCR. No PDF/A, e-sign, HIPAA, or SLA claims here.
CloudConvert: free tier 10 conversions/day, 1 GB, 5 minutes, 5 concurrent, low priority. Credits: time plus base class; only successful conversions charged. Job create is rate-limited (429 + Retry-After). Sandbox is whitelist-only. 99.9% SLA and DPA are their enterprise column, not a RelayPDF claim. This page does not treat a DPA as HIPAA.
Links
Product: https://relaypdf.com/html-to-pdf
Pricing: https://relaypdf.com/pricing
Sibling: https://relaypdf.com/compare/wkhtmltopdf
Docs: https://relaypdf.com/docs/pdf
Options: https://relaypdf.com/docs/options
Docs hub: https://relaypdf.com/docs
CloudConvert: https://cloudconvert.com/CloudConvert HTML to PDF API: https://cloudconvert.com/apis/html-to-pdf
CloudConvert pricing: https://cloudconvert.com/pricing
CloudConvert API v2: https://cloudconvert.com/api/v2
Read HTML to PDF, the wkhtmltopdf compare for engine choice, and the PDF docs for field names.