N8n Binary And Data Official

n8nOfficialPublished by n8n

Skill
Tool integration
Automation and integrations
Apache-2.0
No issues found

From the author

Use when handling files, images, attachments, or binary data in n8n, OR when an AI agent needs to take a user-uploaded file as tool input or return a generated file. For Data Tables (schemas, dedup, persistent state), see the separate n8n-data-tables-official skill. Triggers on "file", "image", "PDF", "attachment", "binary", "upload", "download", chat trigger with files, agent tool that needs a file, vision/multimodal, or any handling of non-JSON file data.

— the description by n8n

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides the essential patterns for managing binary data (files, images, PDFs) within n8n. Because n8n separates data into JSON and binary slots, and because agent tools are restricted to JSON-only communication, this guide explains how to correctly store, pass, and transform files. It covers the critical 'upload-to-storage-and-pass-key' pattern required to bridge the gap between user-uploaded files and AI agent tools, as well as techniques for maintaining binary context through JSON-heavy workflows.

What it does

Explains the separation of JSON and binary data slots in n8n items.
Provides patterns for reading and writing binary data using Code nodes.
Defines the workaround for passing files into and out of AI agent tools.
Details how to preserve binary data through JSON-only operations using Merge nodes.
Outlines requirements for displaying images in chat surfaces via external storage.
Lists common mime types and best practices for file size management.

When to use it

When your workflow needs to process user-uploaded files or attachments.
When an AI agent needs to perform operations on a file via a tool.
When binary data is being stripped during JSON transformations.
When you need to generate a file in a tool and return it to an agent.
When preparing images for display in chat platforms like Slack or Telegram.

Advantages

Prevents common errors where binary data is lost during workflow execution.
Enables complex AI agent capabilities like vision and document processing.
Optimizes performance by using external storage for large files.
Ensures consistent data handling across different n8n nodes.

Usage examples

“How do I pass an image uploaded in a chat trigger to an AI agent tool?”: You must pre-stage the file by uploading it to private storage, then inject the resulting file key into the agent's system prompt so the tool can download it by key.
“My binary data disappears after an Edit Fields node. How do I fix this?”: Use a Merge node set to 'by position' to combine the output of your JSON transformation with the original stream containing the binary data.

Install

Download the skill as a ZIP:
https://autogineer.com/agent-skills/n8n-io/n8n-binary-and-data-official/download

Unzip it into the cross-client skills folder of your project:

mkdir -p .agents/skills && unzip n8n-binary-and-data-official.zip -d .agents/skills

Documentation by n8n

n8n Binary and Data

n8n handles two kinds of data: JSON (in $json) and binary (in $binary), flowing side-by-side. Binary has sharp edges around agent tools, storage, and display contexts (chat surfaces, message rendering).

For tabular storage (Data Tables), see the n8n-data-tables-official skill.

Non-negotiables

Binary is in $binary, not $json. Don't read file contents from $json.
Binary cannot cross the agent tool boundary in either direction. Tool parameters are JSON only (via fromAi()), and tool results are JSON only. Pre-stage binary in storage and pass keys/URLs through JSON. The agent's passthroughBinaryImages: true lets the LLM see uploaded images for vision, but it does NOT enable tools to receive them. See references/AGENT_TOOL_BINARY.md.

Strong defaults

Merge nodes keep binary in context. When a side computation strips binary, merge it back rather than re-fetching. See references/MERGE_FOR_CONTEXT.md.

Binary basics

In n8n, each item has two slots:

{
    json: { ... },           // your data
    binary: {                // your files
        data: {              // 'data' is the typical key; can be any name
            data: '<base64>',
            mimeType: 'application/pdf',
            fileName: 'invoice.pdf',
            fileExtension: 'pdf',
        },
    },
}

$binary.<key> reads the named property. Most file-handling nodes have a binaryPropertyName parameter, the key inside $binary.

Setting binary

File-producing nodes (HTTP Request with binary response, Read Files, etc.) populate $binary automatically. To produce binary in a Code node:

return [{
    json: { ... },
    binary: {
        data: {
            data: Buffer.from(content).toString('base64'),
            mimeType: 'text/plain',
            fileName: 'output.txt',
        },
    },
}]

Reading binary

// In a Code node
const buffer = await this.helpers.getBinaryDataBuffer(0, 'data')
const text = buffer.toString('utf-8')

Most workflows don't need to read binary directly. Pass it through to consumer nodes (email attachments, file uploads, etc.).

See references/BINARY_BASICS.md for more.

Agent tool gymnastics

Agent tools (sub-workflows wired into an AI Agent node or a first-class n8n Agent, or workflows exposed as MCP tools) have a constraint: parameters and results are JSON, not binary. Affects both directions.

Inbound (user uploads → tool consumes): the chat trigger gives files[]. The agent can have passthroughBinaryImages: true for vision, but fromAi() can't pass binary to a tool. So:

Pre-stage uploaded files: hash a key, upload to private storage.
Inject the keys into the agent's system prompt: "Files passed in: [{originalFileName, fileName}]. Use EXACTLY the fileName field when calling tools."
The tool's fromAi('imageName', '...', 'string') receives the key. The sub-workflow downloads from storage.

Outbound (tool produces → agent returns): a tool generates a file. It can't return raw binary.

Generate binary internally.
Upload to storage, get back URL/key.
Return JSON: { ok: true, file_id: '...', url: '...' }.
The agent embeds the URL in its response, or another tool fetches by key.

For the full pattern including the async-via-webhook variant for long-running tools, see references/AGENT_TOOL_BINARY.md.

Merge for keeping binary in context

A JSON-only operation (Edit Fields, Code, IF) often strips binary from the item. To keep it:

[Source with binary] ─┬─→ [Edit Fields: transform JSON] ─┐
                      │                                    ├─→ [Merge: by position] ─→ [Email with attachment]
                      └─────────────────────────────────────┘

Merge combines the streams, and binary survives. See references/MERGE_FOR_CONTEXT.md.

CDN requirement for chat surfaces

When a workflow generates an image and the user wants it embedded in a chat message (Slack, Discord, Teams, Telegram, embedded webhook chat, etc.):

Binary on the item isn't enough. Chat surfaces don't read $binary; they render messages that reference images by URL (or via platform-specific file upload APIs).
The image must live somewhere a URL can fetch. Upload to a CDN or object store first.
The user configures this storage. Not built into n8n.

Common options span object storage (S3, R2, GCS, Azure Blob, Vercel Blob, Supabase Storage) and drive-style services (Dropbox, Google Drive, OneDrive, Box). Ask the user what they use rather than defaulting to S3.

See references/CDN_REQUIREMENT.md.

Data Tables

For Data Tables, see the n8n-data-tables-official skill. Distinct surface with its own gotchas (default columns, no foreign keys, no JSON column type, manual-mapping UI quirk).

Reference files

File	Read when
`references/BINARY_BASICS.md`	First time handling binary, or reading/writing the `$binary` slot
`references/AGENT_TOOL_BINARY.md`	Agent tool needs a user-uploaded file, or produces a file (the boundary in either direction)
`references/MERGE_FOR_CONTEXT.md`	Binary disappears after a JSON transform and needs to re-attach
`references/CDN_REQUIREMENT.md`	Showing images in a chat surface or other places that need URL-referenced images

Anti-patterns

Anti-pattern	What goes wrong	Fix
Trying to read file content from `$json`	Binary isn't in `$json`	Use `$binary`
Building an agent tool that returns binary directly	Tool output is JSON-only, so binary doesn't survive	Upload to storage, return key/URL in JSON (see `AGENT_TOOL_BINARY.md`)
Trying to pass uploaded chat files into a tool via `fromAi`	`fromAi` doesn't carry binary, so the tool gets nothing	Pre-stage uploads to storage, inject keys in the system prompt, and have the tool download by key
Setting `passthroughBinaryImages: true` and assuming tools can now see the file	The flag only affects what the LLM sees, not what tools receive	Still need the upload-and-pass-key pattern for tools
Losing binary after a JSON transform	The transform's output item doesn't have binary	Use Merge to combine the JSON output with the binary stream
Storing image in n8n binary and expecting a chat surface to display	Chat surfaces need URL-accessible images (or a platform-native file upload), not raw `$binary`	Upload to CDN, embed URL or use the platform's file API
Hardcoding binary base64 in a Code node	Massive workflow JSON, slow, leaky	Reference binary via `$binary` properly, or upload to storage and reference by URL

Files

ATTRIBUTION.mdAdded by AutoGineer862 B
LICENSELicence file added by AutoGineer11.0 KiB
SKILL.md7.1 KiB
references/AGENT_TOOL_BINARY.md17.3 KiB
references/BINARY_BASICS.md4.8 KiB
references/CDN_REQUIREMENT.md4.6 KiB
references/MERGE_FOR_CONTEXT.md3.7 KiB

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Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs Node.js

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Attribution and licence

Published by

n8n

Publisher

n8n (Official)

Source

n8n-io/skills · skills/n8n-binary-and-data-official · commit 27b6b9f

Licence

Apache License 2.0 (redistribution allowed)

LICENSE (added by AutoGineer from LICENSE)
ATTRIBUTION.md (written by AutoGineer)

Synced

2026-11-09

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