OneTaskBy Tim King · Updated
Fill PDF Form
Fill In Fillable PDF Text Boxes, Checkboxes and Dropdowns in Your Browser
OneTask is free, with no sign-up, and built by one person.
If this tool saved you time, a coffee helps keep new ones coming.
How the Fill PDF Form works
Fill PDF form fields without a desktop reader. Drop in a fillable PDF and the tool lists every field with its current value. Type one answer per line, such as "name = Alice", and download the completed form. It all runs in your browser, so your answers are never uploaded.
Fillable PDFs are everywhere: job applications, visa forms, tax returns, rental agreements, school trip consent slips and insurance claims. Each one is a normal page with interactive fields laid on top, defined by the AcroForm part of the PDF standard. A full desktop reader is the usual way to fill them, but not every computer has one, and many browser viewers can display a form without saving the answers properly.
How to fill PDF form fields here
- Drop the PDF on the tool. Every field appears in the results with its name, the kind of answer it takes and what it holds now.
- In the Answers box, write one line per field you want to set, as
field name = value. Field names are matched without regard to capital letters. - The completed PDF is ready to download as soon as the lines are valid. Change a line and it updates at once.
| Field kind | What to type | Example |
|---|---|---|
| Text box | Any text | Surname = Okafor |
| Checkbox | yes or no (also y, n, true, false, x) | Agree = yes |
| Dropdown or list | One of the listed options | Country = UK |
| Radio buttons | One of the listed options | Title = Ms |
Leave out any field you do not want to change. To clear a text box, write its name followed by an equals sign and nothing after it.
How the PDF form filler works
The file is opened with pdf-lib, an open-source PDF library, inside your browser. The tool reads the form's fields and checks each line against them: the field must exist, must not be marked read-only, and the value must fit. Checkboxes need a yes or no, choice fields need one of their own options, and text fields respect a maximum length if the form sets one. Anything that does not fit is listed in a single message so you can fix every line at once.
When all the lines pass, each field's value is set and its appearance is redrawn so it shows in any viewer, then the file is saved. With Flatten the answers chosen, the answers are drawn into the page and the fields are removed, so nobody can change them.
Tips and pitfalls
Odd field names. Forms are often built with names like Text1 or
topmostSubform[0].Page1[0].f1. The list shows the real names in page order, so copy them exactly
as shown, including any brackets and dots. Matching ignores case
but not spaces or punctuation.
Scanned forms have no fields. A form that was printed and scanned, or exported as a flat PDF, is just a picture of boxes. The tool will say there are no fillable fields. Add text to it with a PDF editor or annotate it instead.
Signatures. A signature field needs a digital certificate or a drawn signature. This tool skips signature fields; sign the completed file with a signing tool afterwards.
Scripts and calculations. Some forms run JavaScript to total amounts or format dates when you leave a field. Those scripts do not run here, so type totals yourself in the format the form expects.
Flatten last. Flattening is permanent. Keep an unflattened copy until you are sure every answer is right.
How to read the result
The results list each field as name (kind) with its value after your changes, then how many fields
were filled and the new file size. Open the download in any PDF viewer to check the answers sit
where you expect before sending it.
FAQ
How do I know if a PDF is fillable?
Drop it on the tool. A fillable PDF lists its fields straight away. If you see a message that there are no fillable fields, the boxes are only drawn on the page, which is common with scanned and printed forms.
Can I save a filled PDF form and edit it later?
Yes, as long as you keep the fields editable. The answers are saved in the fields, so you can open the downloaded file here or in any reader and change them. Flattened answers are fixed into the page for good.
Why don't my answers show in some viewers?
Some viewers show a stored appearance rather than a field's value. This tool redraws the appearance for every field it fills, so answers show in browsers, phones and printers. Flattening makes that certain.
Is my form uploaded anywhere?
No. The PDF is read and filled entirely by your browser on your device. Forms often hold addresses, dates of birth and ID numbers, and none of it is sent to a server.
See also: all PDF tools, Images, Audio, Video & Screen, SVG, Simulations & Screensavers, Generative Art, Chart Makers, 3D Model Viewers, Drawing Pads, Mockups & 3D Making, Diagram Makers, 3D Science, Tracker Music.
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