Working with files

Every Nitro action takes a file and returns either a file or structured data. Zapier’s file handling makes both ends easier than they are in most integrations, with a few things worth knowing.

Getting files in

Zapier represents a file either as a file object or as a URL. The Nitro app accepts both: if a step hands it a URL, the app downloads the file first and then uploads it to Nitro. You do not need a separate download step.

Source	Field to map into the Nitro step
Google Drive, Dropbox, Box, OneDrive	The trigger’s or search step’s file field
Gmail / Outlook / Email by Zapier	The attachment field
Webhooks by Zapier	A URL in the payload, mapped straight into the file field
Formatter, Files by Zapier	The produced file object
A previous Nitro action	Its file output, such as Compressed PDF File

Only the file’s bytes reach Nitro — its name is not passed through. Set the name on the step that writes the result instead.

Getting results out

Files

With Output Type set to Download file, the action returns a file object under a labelled field such as Compressed PDF File or Merged PDF File. Map that field into any file-accepting input: a Drive upload, a Dropbox upload, a Gmail attachment, or the file input of another Nitro action.

URLs and metadata

With Download URL, the action returns:

Field	Description
`file_url`	Download URL for the output
`content_type`	MIME type of the output
`file_size_bytes`	Size in bytes
`page_count`	Pages in the output

Use this when you want the metadata — for example, to record how much a compression saved, or to branch on page count — or when the destination app takes a URL rather than a file.

Output URLs are valid for about 15 minutes; Nitro then deletes the file. Consume the URL in the same Zap run rather than storing it in a database or sheet.

Chaining actions

Nitro actions chain by mapping one step’s file output into the next step’s file input. With Download file on each step, a scan-to-archive Zap looks like:

Ocr PDF

PDF File → the trigger’s file. Language → the document’s language.

Optimize PDF

PDF File → OCR PDF File from step 1. Optimization Profile → Archive.

PDF to PDF/A

PDF File → Optimized PDF File from step 2. Leave the conformance level at 2b.

Google Drive — Upload File

File → PDF/A File from step 3.

Two pairs of actions are designed to chain through their structured outputs:

Smart PII Detection or Text Bounding Box Extract → Redact PDF

Both extraction actions emit a Redactions JSON field shaped exactly like Redact PDF’s Redactions JSON input. Map it straight across:

Smart PII Detection — PDF File → the source document.
Redact PDF — PDF File → the same source document; Redactions JSON → step 1’s Redactions JSON.
Upload Redacted PDF File wherever the original is not.

To redact only some matches, use Filter by Zapier on pii_types[] or route the redactions[] line items through a Formatter step before mapping.

Automated PII detection is not exhaustive. Review pii_count and pii_types[], and keep a human check in the loop for anything sensitive.

Smart Detect Form Fields → Add Fillable Form Fields

Add Fillable Form Fields takes five parallel lists. Map the matching Smart Detect Form Fields outputs into each — the picker passes one entry per detected field, so the counts line up automatically:

Add Fillable Form Fields input	Smart Detect Form Fields output
Page Indices	Page Index
Field Types	Field Type
Field Names	Field Name
Bounding Boxes	Bounding Box [x, y, width, height]
Field Values (optional)	Value

PDF File on both steps is the same source document. You can also type the lists by hand — one row per field, with each bounding box as x, y, width, height in points.

Multi-file outputs

PDF to Image and Split PDF produce several files.

With Download file, the result is a single ZIP archive. Zapier has no built-in unzip action, so this is usually the harder path.
With Download URLs, the result carries a list of URLs — file_urls[] and a files[] line-item group with URL, contentType, and metadata per file, plus first_url for the common case of only needing page one.

Both actions default to Download URLs for this reason. To store every output file, loop over the line-item group with Looping by Zapier and upload each URL in turn — within the 15-minute window.

Renaming outputs

Nitro does not set a meaningful output file name, so name the file on the step that writes it. A Formatter by Zapier → Text step is the usual way to build one from the trigger’s file name — for example stripping the extension and appending -compressed.pdf. When converting between formats, remember to change the extension: a PDF to Microsoft Office output saved as .pdf will not open in Word.

Input formats by action

Most options are dropdowns or plain fields. These are the ones with a format to get right. Page indices are zero-based everywhere.

Action	Field	Format
Text Extract, Delete PDF Pages, Ocr PDF, Watermark PDF	Page Indices	Comma-separated: `0,2,5`
Rotate PDF	Page Indices / Rotation Amounts	Two lists; one amount applies to all pages, or one amount per page
Split PDF	Page Indices (JSON)	Array of arrays: `[[0,2],[1,3,4]]` — each inner array becomes one PDF
Redact PDF	Redactions JSON	`[{"pageIndex":0,"boundingBox":[100,100,200,120]}]` — box is `[x, y, width, height]` in points
Watermark PDF	Bounding Box	`x0,y0,x1,y1` corner coordinates in points, e.g. `210,10,290,60`
Text Bounding Box Extract	Texts to Search / Regex Flags	Comma-separated; flags are `ignore-case`, `multiline`, `dot-all`
Add Fillable Form Fields	Bounding Boxes	One row per field: `x, y, width, height`
Fill PDF Form	Field Mappings	One row per field: field name → value. Checkboxes accept `true`, `yes`, `1`, `x`
Fill PDF Form	Form Data File	CSV (header row then a values row), JSON, XFDF or FDF — see below

Fill PDF Form data files

The data file is passed to Nitro as-is, so it must be in a shape the API accepts:

JSON
CSV
XFDF / FDF

A list of field/value objects — not a flat object:

[
  { "field": "first_name", "value": "Jane" },
  { "field": "last_name",  "value": "Doe" },
  { "field": "is_active",  "value": true }
]

Build it with a Code by Zapier or Formatter step if the source gives you a flat object, or skip the file and use inline Field Mappings instead.

first_name,last_name,is_active
Jane,Doe,yes

For a handful of values, inline Field Mappings is simpler than a file: one row per field, mapped from the trigger. Provide the file or the mappings, not both.

Overview

Get started

Actions

Reference

Getting files in

Getting results out

Files

URLs and metadata

Chaining actions

Multi-file outputs

Renaming outputs

Input formats by action

Fill PDF Form data files

​Getting files in

​Getting results out

​Files

​URLs and metadata

​Chaining actions

​Multi-file outputs

​Renaming outputs

​Input formats by action

​Fill PDF Form data files

Getting files in

Getting results out

Files

URLs and metadata

Chaining actions

Multi-file outputs

Renaming outputs

Input formats by action

Fill PDF Form data files