JustFill and Filly AI both use AI to detect fields on a PDF and fill them for you, so at first glance they look interchangeable. They aren't. JustFill is a fast, pay-as-you-go tool for filling a document; Filly AI is a workflow for filling every form for a client — reusing their details, pulling from a built-in library of real government forms, and collecting a signature at the end.
Choose JustFill if you occasionally fill a one-off PDF and want to pay per use — it detects fields on scanned or flattened PDFs, lets you paste text or dictate values, and charges in credits (about $7 per 25 fills). Choose Filly AI if you fill forms repeatedly for clients: it saves each client’s details as a reusable profile, includes ready-to-fill government forms (W-9, W-4, I-9) and 25 templates, fills Word documents as well as PDFs, and sends no-login e-sign links. Filly has a free plan with 10 AI fills a month; paid plans start at $19/month.
What’s the core difference?
JustFill is document-centric: you bring a PDF, it finds the fields, you fill it, you download it. Filly AI is client-centric: you save a person’s details once, and then any form you upload — or any government form from the built-in library — fills itself from that profile. For anyone who types the same name, date of birth, and address into 20 or 30 forms per client, that difference is the whole point. Small firms already lose so much time to admin that UK research by Sage found they effectively work a 13th month each year on it.
Filly AI vs JustFill: feature comparison
| Feature | Filly AI | JustFill |
|---|---|---|
| AI field detection on scanned / flattened PDFs | Yes — via OCR + AI | Yes |
| Fills Word (.docx) documents | Yes | No — PDF and image only |
| Reusable client profiles | Yes — save a client once, fill every form from it | No — generic saved “snippets,” not client records |
| Built-in government-form library | Yes — W-9, W-4, I-9 and more, plus 25 templates | No — template library not yet available |
| E-signature | Yes — no-login link, recipient signs in the browser | No |
| Batch fill (one form, many people) | Yes | Yes |
| Paste text / dictate to fill | Fills from saved profiles and uploads | Yes — paste notes or dictate by voice |
| Free plan | Yes — 10 AI fills/month, no credit card | Manual fill only; AI detection needs paid credits |
| Pricing | Free, then $19/month | Pay-as-you-go (~$7 per 25 fills) or $19/month |
| Install required | No — runs in the browser | No — runs in the browser |
When is JustFill the better choice?
If you fill PDFs only now and then, JustFill’s pay-as-you-go pricing is a lower commitment than any monthly plan — you buy a pack of fills and stop when you’re done. It also has two genuinely handy input methods Filly doesn’t: you can paste a block of unstructured text (an email, notes, a CV) and let the AI map it to fields, and you can dictate values by voice in several languages. For a one-off flattened PDF where you just need fields drawn and filled quickly, it does that well.
When is Filly AI the better choice?
If the same forms come across your desk for different people — client intake, immigration and tax forms, contracts, onboarding packets — a per-document tool makes you re-enter the same data every time. Filly saves each client once and fills from that profile, so the retyping disappears. It also covers the parts JustFill leaves out: real government forms are built in and ready to fill, Word documents are supported alongside PDFs, and every completed form can be sent for signature with a link the recipient opens in their browser — no account required. That last step matters, because about 79% of e-signed agreements are completed within 24 hours, versus days for print-and-scan.
Which one is cheaper?
It depends on volume. For a handful of fills a year, JustFill’s credit packs (about $7 per 25 fills) are cheaper than any subscription. For steady, repeated form work, Filly’s $19/month covers unlimited-feeling volume with reusable profiles and e-sign included — and its free tier (10 AI fills/month) lets you actually test the AI before paying, which JustFill’s free tier (manual only) doesn’t. See Filly’s pricing.
Frequently asked questions
Are Filly AI and JustFill the same kind of tool?
They overlap on AI field detection, but they’re built for different jobs. JustFill is a fill utility priced per use; Filly AI is a form-filling workflow with client profiles, a government-form library, Word support, and e-signature. If you fill forms for other people repeatedly, that workflow is the difference.
Does JustFill support Word documents or e-signature?
No. JustFill works with PDFs and images and does not fill Word files or collect signatures. Filly AI fills Word (.docx) documents and sends no-login e-sign links.
Does Filly AI have ready-made government forms?
Yes. Filly includes fillable versions of common government forms such as the W-9, W-4, and I-9, plus 25 contract and business templates — you pick one and it fills from a saved profile. JustFill’s public template library is not yet available.
Can I try the AI for free?
With Filly, yes — the free plan includes 10 AI fills a month with no credit card. JustFill’s free tier only allows manual field drawing; its AI detection requires paid credits. Try Filly on a ready-made template or upload your own form.