Appending to a File
Overview
This guide walks you through appending content to an existing file on the Hedera network using the Transaction Tool. The file append process allows you to add data to a file that's already stored on the Hedera File Service. This is particularly useful when dealing with large files that exceed the single transaction size limit, as you can split the content into chunks and append them sequentially.
Prerequisites
Before you begin, you should have completed the following:
Transaction Tool Setup: Follow the New User Installation Guide or Install: Existing Users.
User Account Configuration: Complete the Account Setup process to create user account.
You should also have:
File ID: The unique identifier of the file you want to append to (format: 0.0.xxxxx)
Payer Account: An account with sufficient HBAR balance to pay transaction fees
Signing Authority: Access to ALL keys in the current file's key list
File Content: The data you want to append to the existing file
Understanding File Append Permissions
File append operations have strict signature requirements:
Required Signatures:
All the keys in the file's current key list must sign the append transaction.
If the file has multiple keys or a threshold key, all required signatures must be collected.
Transaction Size Limits
When appending content to files, be aware of these limitations:
Single Transaction Limit: Each append transaction must remain within the total transaction size limit (typically 6,144 bytes)
Maximum File Size: The total file size after all appends must not exceed the network limit (typically 1,048,576 bytes)
Chunking Strategy: For large files, split your content into appropriately sized chunks and submit multiple append transactions.
Transaction Properties
Payer ID
The Hedera account ID that will pay the transaction fees. Must have sufficient HBAR balance.
Yes
0.0.6518491 - View examples on HashScan
Valid Start
The date and time the transaction should be submitted to the network.
Yes
2025-04-05T10:00:00Z
Max Transaction Fee
The maximum amount of HBAR you're willing to pay for the transaction. If the required fee exceeds this value, the transaction will fail.
Yes
2 HBAR (Default)
Transaction Memo
Optional text description attached to the transaction
No
Appending configuration data
File Append Properties
File ID
The unique identifier of the file you want to append content to
Yes
0.0.12345
Signature Key
The current key(s) that must sign the append transaction. ALL keys in the file's key list are required.
Yes
121c3e1bd....
Chunk Size
The size of each chunk when splitting large content for multiple append operations
Optional
4096 bytes (Default)(recommended for large files)
Upload File
Upload a local file whose contents will be stored on the Hedera network. Or Enter the File Content manually
Optional
config.json
Step-by-Step Guide
Step 1: Navigate to the File Create Transaction interface
You can access the Append File form in three ways:
Method 1 – Using the Main Menu
Select Create New, then choose Transaction.
Select File, then choose Append File.
Method 2 – From the left navigation panel
Select Files.
On the Files page, select Add New then choose Append from the dropdown menu.
Method 3 – From the list of Files
Select Files, then in the list, select the file you want to append to.
On the right-hand side, the File Information is displayed. Select Append.
Step 2: Configure Transaction Properties
Fill in the required file parameters in the form. Refer to the Transaction Properties and File update properties table above for descriptions and examples.
Step 3: Submit the Transaction
Select Sign and Execute on the top right corner.
In the authentication prompt, confirm the transaction:
If you set up the Transaction Tool using an email address and password, you will be prompted to enter your application password
If you set up the Transaction Tool using the keychain option, the transaction executes automatically. However, if you haven’t recently entered your keychain password, a system prompt may appear before execution.
The system processes the transaction and appends the content to the file on the Hedera network.
Step 4: Handle Large Files (Multiple Appends)
If your content is too large for a single transaction:
Calculate chunks: Divide your total content size by the chunk size (typically 4KB).
Submit first append: Start with the first chunk of data.
Wait for confirmation: Ensure each append succeeds before proceeding.
Continue appending: Submit subsequent chunks in order.
Verify completion: After all chunks are appended, verify the complete file content.
Step 5: View the Updated File
Once the transaction is successful:
The transaction details will be displayed with the confirmation.
You can view the appended file details in the following locations:
Transaction History: View the append transaction record with the File ID.
Files Page: The file appears in your files list with its updated size.
File Details: Select the file to view its complete metadata and current size.
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