Isn't self-hosting Stirling PDF more private than AttachKit?

When you self-host Stirling correctly, your files stay entirely on your own infrastructure — that's genuinely strong, and being open-source means you can audit exactly what it does. The trade-off is that it's only as private and secure as your deployment (you host, secure, and update it). AttachKit gives you no-upload privacy with nothing to run or maintain: the file is processed in your browser, which you can verify in the Network tab. Different paths to the same goal — total control vs. zero setup.

Is AttachKit open-source like Stirling PDF?

No — AttachKit is not open-source, and that's a real point in Stirling's favour if openness and auditability are priorities for you. What AttachKit offers instead is verifiable behaviour in the browser: because the file is processed client-side, you can open your Network tab and confirm nothing is uploaded, without needing the source code or your own server.

When should I use Stirling PDF instead of AttachKit?

When you want open-source software you can audit and run entirely on your own infrastructure, the widest possible set of PDF operations (~50 tools), or full control over hosting — Stirling is excellent for that, and the right pick for many developers and self-hosters. AttachKit is for when you'd rather not run anything: zero-install in any browser, no-upload by architecture, plus AI auto-fill and offline-verifiable signatures.

Alternative · Stirling PDF

AttachKit vs. Stirling PDF — self-hosted open-source vs. zero-install in any browser

Stirling PDF: A self-hosted, open-source PDF toolbox — ~50 tools you run yourself via Docker.

Stirling PDF is the privacy-conscious developer's pick, and for good reason: it's genuinely open-source (you can read and audit every line) and fully self-hostable, so when you run it yourself your files stay entirely on your own infrastructure, across ~50 tools. That openness and control is real, and we won't undersell it — if you want to own the whole stack, Stirling is excellent. AttachKit makes a different trade: there's nothing to self-host, no Docker, no server to maintain — it runs in any browser instantly, with the file processed on-device and never uploaded, plus AI auto-fill and offline-verifiable signatures. The honest catch on our side: AttachKit is not open-source.

Why pick AttachKit for these cases

Nothing to self-host, no Docker, no server to maintain — runs in any browser instantly.
Stirling is fully open-source and self-hostable (a genuine advantage if you want to own the stack); AttachKit's privacy is architectural — the file never leaves your browser.
AI auto-fill from a saved profile, which Stirling doesn't offer.
An offline-verifiable signature anyone can check without running anything.

Side-by-side

A marks the side with the genuine advantage on that row — honestly, including the few where Stirling PDF wins.

Openness & control

Stirling PDFFully open-source and self-hostable — you can audit the code and run it entirely on your own infrastructure. Maximum control.

AttachKitNot open-source. Privacy comes from architecture instead — the file is processed in your browser and never uploaded, which you can confirm in the Network tab.

Setup & maintenance

Stirling PDFYou run it — typically a Docker container you deploy, host, secure, and keep updated (or use a paid hosted plan).

AttachKitNothing to host or install — open it in any modern browser, on any OS, and start.

Where your PDF goes

Stirling PDFOn a self-hosted instance, nowhere external — it stays on your server. (Quality depends on your deployment being secured and updated.)

AttachKitNowhere — it stays in your browser tab; nothing is uploaded, and there's no server for you to secure.

Price

Stirling PDFSelf-host is free for small use (historically ≤5 users); paid Server ~$99/mo, Enterprise ~$12/user/mo, or hosted ~$0.05/doc, as of 2026.

AttachKitFree: unlimited fill + 15 signed PDFs/mo, no infrastructure. Pro $12/mo (or $120/yr — $10/mo), flat.

Tool breadth

Stirling PDF~50 tools — convert, merge/split, OCR, compress, sign, redact, and many niche operations, all self-hosted.

AttachKitA focused browser-side toolkit — fill, sign, redact, convert, compress, merge/split, watermark, OCR, compare — fewer tools, none uploaded, nothing to run.

AI auto-fill from your profile

Stirling PDFNo saved-profile AI autofill (some tools have regex-based PII patterns, but not AI form-fill).

AttachKitSave your details once; AI fills any form from your profile, with the PDF staying on-device — only field labels go to the model.

Verifiable signatures

Stirling PDFSign and certificate-validate PDFs on your own instance.

AttachKitSelf-sign in-browser plus an offline-verifiable signature anyone can check on any device, free — no instance to run.

	Stirling PDF	AttachKit
Openness & control	Fully open-source and self-hostable — you can audit the code and run it entirely on your own infrastructure. Maximum control.	Not open-source. Privacy comes from architecture instead — the file is processed in your browser and never uploaded, which you can confirm in the Network tab.
Setup & maintenance	You run it — typically a Docker container you deploy, host, secure, and keep updated (or use a paid hosted plan).	Nothing to host or install — open it in any modern browser, on any OS, and start.
Where your PDF goes	On a self-hosted instance, nowhere external — it stays on your server. (Quality depends on your deployment being secured and updated.)	Nowhere — it stays in your browser tab; nothing is uploaded, and there's no server for you to secure.
Price	Self-host is free for small use (historically ≤5 users); paid Server ~$99/mo, Enterprise ~$12/user/mo, or hosted ~$0.05/doc, as of 2026.	Free: unlimited fill + 15 signed PDFs/mo, no infrastructure. Pro $12/mo (or $120/yr — $10/mo), flat.
Tool breadth	~50 tools — convert, merge/split, OCR, compress, sign, redact, and many niche operations, all self-hosted.	A focused browser-side toolkit — fill, sign, redact, convert, compress, merge/split, watermark, OCR, compare — fewer tools, none uploaded, nothing to run.
AI auto-fill from your profile	No saved-profile AI autofill (some tools have regex-based PII patterns, but not AI form-fill).	Save your details once; AI fills any form from your profile, with the PDF staying on-device — only field labels go to the model.
Verifiable signatures	Sign and certificate-validate PDFs on your own instance.	Self-sign in-browser plus an offline-verifiable signature anyone can check on any device, free — no instance to run.

Switching questions, answered

Isn't self-hosting Stirling PDF more private than AttachKit?: When you self-host Stirling correctly, your files stay entirely on your own infrastructure — that's genuinely strong, and being open-source means you can audit exactly what it does. The trade-off is that it's only as private and secure as your deployment (you host, secure, and update it). AttachKit gives you no-upload privacy with nothing to run or maintain: the file is processed in your browser, which you can verify in the Network tab. Different paths to the same goal — total control vs. zero setup.
Is AttachKit open-source like Stirling PDF?: No — AttachKit is not open-source, and that's a real point in Stirling's favour if openness and auditability are priorities for you. What AttachKit offers instead is verifiable behaviour in the browser: because the file is processed client-side, you can open your Network tab and confirm nothing is uploaded, without needing the source code or your own server.
When should I use Stirling PDF instead of AttachKit?: When you want open-source software you can audit and run entirely on your own infrastructure, the widest possible set of PDF operations (~50 tools), or full control over hosting — Stirling is excellent for that, and the right pick for many developers and self-hosters. AttachKit is for when you'd rather not run anything: zero-install in any browser, no-upload by architecture, plus AI auto-fill and offline-verifiable signatures.

Try AttachKit now

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