API2PDF and RelayPDF are both hosted document APIs. Both wrap Headless Chrome (Chromium), wkhtmltopdf, and LibreOffice so you do not install those binaries, patch them, or size the workers. The products differ in how they expose the engines, how they bill, and what sits around the render call.
If you need an API2PDF alternative, start with the feature table, then the two billing models. API2PDF wins some cells. RelayPDF wins others. Neither page below invents ratings.
Feature table
Public pages as of 23 August 2026. Yes means the vendor documents the capability. Gaps are labeled as not advertised, not as a secret missing feature.
| Capability | RelayPDF | API2PDF |
|---|---|---|
| HTML to PDF | Yes. POST /v1/pdf, html as UTF-8 JSON (not Base64). Chromium. | Yes. /chrome/pdf/html or /wkhtmltopdf/html. Engine is the path. |
| URL to PDF | Yes. Public http(s) only. Private and loopback hosts rejected. | Yes. Chrome and wkhtml URL routes. extraHTTPHeaders for gated pages. |
| Markdown to PDF | Yes. GFM Markdown on the same /v1/pdf endpoint. | Yes on the v2 Node client (chromeMarkdownToPdf). Not a homepage hero. |
| Office to PDF | Yes. POST /v1/convert (LibreOffice). Word, Excel, PPT, ODF, CSV, images, email. Targets PDF, DOCX, XLSX, HTML, PNG. | Yes. POST /libreoffice/pdf. Homepage: Word, PowerPoint, images. Clients also list more Office pairs. |
| Screenshots | Yes. POST /v1/images. HTML or URL to png, jpeg, webp. | Yes. Chrome image endpoints plus Office thumbnails. |
| Merge PDFs | Yes. POST /v1/pdf/merge, 2-20 files. Tool inputs 15 MB. | Yes. Homepage merge (PdfSharp in the Node client). |
| PDF forms | Yes. /v1/pdf/form/fields and /form/fill (AcroForm, flatten). | Not advertised on the homepage or FAQ. Password, extract, merge, bookmarks are. |
| MCP | Yes. First-party stdio MCP for Cursor and Claude. Contents not logged. | No first-party MCP. REST and language clients. Third-party wrappers are not the product. |
| Prepaid / billing | Prepaid wallet. Per-operation rates. Failures not billed. Credit never expires. $5 signup, no card. | Pay as you go: $1 / month plus $0.001 / MB and $0.00019551 / sec. Auto-refill. One free trial month. No published per-document price. |
What each product actually is
API2PDF homepage line is accurate: Headless Chrome, wkhtmltopdf, and LibreOffice in one serverless REST API. Endpoints are named after the engine. Production Chrome is version 130. Options include landscape, printBackground (default false), headers, page ranges, delay, and wait methods. Results return as a FileUrl kept 24 hours unless you send them to your storage.
RelayPDF is a managed Chromium API first. POST /v1/pdf accepts exactly one of html, url, markdown, or templateId. Office and wkhtmltopdf go to POST /v1/convert. Tools are separate routes. One bearer key covers REST, SDKs, CLI, and MCP. Response modes: binary (default), url (24-hour download), or async.
Both products are honest about the engine mix. API2PDF is more explicit at the URL. RelayPDF is more explicit about defaulting HTML work to Chromium and treating wkhtmltopdf as a convert engine.
Where API2PDF wins
Large jobs. API2PDF FAQ: no specific file-size cap, 2 GB RAM, 90 seconds, GB-sized PDFs, V2 XL if needed. RelayPDF Chromium timeout is 60 seconds and tool inputs are 15 MB. API2PDF published envelope is larger.
Rate limits. API2PDF says it does not set request-rate limits. RelayPDF does (burst 5 / 10s, trial 20 / min, funded 60 / min). API2PDF public stance is more permissive for bursts.
Authenticated URL fetch. API2PDF documents extraHTTPHeaders. RelayPDF fetches public URLs only. If the page is behind a header gate, API2PDF documents a path.
Self-host. API2PDF says the API is available as a Docker container in your cloud. RelayPDF is the managed side of that tradeoff. If the worker must stay in your VPC, API2PDF advertises that conversation.
Pricing. API2PDF: $1 / month plus $0.001 / MB and $0.00019551 / sec. A 2-second, 0.2 MB PDF is a fraction of a cent plus the dollar. RelayPDF Chromium PDF or screenshot is $0.015 per success. API2PDF can win on unit cost. The bill varies with time and bytes.
Where RelayPDF wins
One PDF route. HTML, public URL, GFM Markdown, and Handlebars templates share POST /v1/pdf. printBackground defaults to true. Formats include letter, legal, tabloid, ledger, A0-A6. waitUntil defaults to networkidle0. Timeout 60s. Failed renders are not billed.
Prepaid wallet. Successful operations debit cents. Failures never debit. Credit never expires. Packs add 5-15 percent. API2PDF can hold a balance too, but the meter is bandwidth plus compute plus $1 / month after day 30.
PDF tools. RelayPDF: merge (2-20), extract, AES-256 protect, stamp, rotate, compress, info, text (no OCR), AcroForm fill, barcodes, zip. API2PDF: merge, extract, password, thumbnails, barcodes, zip. Form fill is the RelayPDF cell.
Agents. First-party MCP and CLI cover pdf, image, convert, tools, templates, and jobs. Official SDKs share REST field names. API2PDF has solid language clients. It does not ship first-party MCP.
Engines, not brands
wkhtmltopdf is useful for old HTML. It is a poor default for Flex, Grid, or modern JavaScript. Both vendors still expose it. RelayPDF defaults to Chromium and keeps wkhtmltopdf on /v1/convert. API2PDF keeps it as a peer of Chrome, which makes engine A/B tests obvious.
LibreOffice is the Office engine on both sides. Compare real files. RelayPDF: $0.04 convert, $0.025 wkhtmltopdf. API2PDF folds Office into compute and bandwidth.
When to use which
Stay on API2PDF when
- You already call chrome, wkhtmltopdf, or libreoffice routes and the FileUrl flow works.
- Jobs need more than 60 seconds or more than RelayPDF 15 MB tool-input cap.
- You rely on extraHTTPHeaders or a self-hosted container.
- You prefer a $1 monthly floor plus usage over a prepaid per-operation card, and your files are small and fast.
Move to RelayPDF when
- You want one POST /v1/pdf for HTML, URL, Markdown, and templates, with Chromium print options and binary by default.
- You need AcroForm fill, stamp, or the rest of the $0.005 tool set in the same key as render.
- Coding agents should call a first-party MCP server instead of wrapping REST.
- You want prepaid cents per successful document and a ledger that never bills failures.
Do not rip out a working API2PDF integration on a Friday. Port one real document and compare bytes and CSS.
Limits (both)
RelayPDF: public URLs only, 60s Chromium timeout, 15 MB tool inputs, merge 2-20, funded 60 writes / minute. /v1/pdf/text is not OCR. No PDF/A, e-sign, HIPAA, or SLA claims here.
API2PDF: 24-hour file retention, 90s / 2 GB unless XL. $1 monthly minimum after the trial month; FAQ says no refunds on that floor. Pricing-page privacy language is not treated as HIPAA or SOC 2 here. printBackground defaults to false.
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 · API2PDF: https://www.api2pdf.com/ · API2PDF pricing: https://www.api2pdf.com/pricing · API2PDF FAQ: https://www.api2pdf.com/faq
Read HTML to PDF, the wkhtmltopdf compare for engine choice, and the PDF docs for field names.