---
title: account_compress
description: Compresses an account to save storage space with state proof
source_url:
  html: https://thru.org/docs/spec/vm/syscalls/account_compress/
  md: https://thru.org/docs/spec/vm/syscalls/account_compress.md
---

# account_compress

## Overview

The `account_compress` syscall compresses an account by setting the COMPRESSED flag and providing a state proof. This allows the account data to be stored more efficiently while maintaining verifiability.

## Syscall Code

**Code:** `0x08` (`TN_SYSCALL_CODE_ACCOUNT_COMPRESS`)

## C SDK Function

```c
ulong tsys_account_compress(ulong account_idx, void const* proof, ulong proof_sz);
```

## Arguments

**`account_idx` · *ulong* · **required****

Index of the account to compress. Must be writable in the transaction.

**`proof` · *void const** · **required***\*

Pointer to the state proof data.

**`proof_sz` · *ulong* · **required****

Size of the state proof data in bytes.

## Return Value

Returns a syscall result code:

**`Success` · *ulong***

- `TN_VM_SYSCALL_SUCCESS` (0) - Account compressed successfully
- `0` (special case) - Ephemeral account deleted instead of compressed

**`Error Codes` · *ulong***

- `TN_VM_ERR_SYSCALL_INVALID_ACCOUNT_INDEX` (-8) - Account index out of bounds
- `TN_VM_ERR_SYSCALL_ACCOUNT_DOES_NOT_EXIST` (-9) - Account does not exist
- `TN_VM_ERR_SYSCALL_ACCOUNT_NOT_WRITABLE` (-10) - Account not writable in transaction
- `TN_VM_ERR_SYSCALL_TXN_HAS_COMPRESSED_ACCOUNT` (-37) - Transaction already has a compressed account
- `TN_VM_ERR_SYSCALL_ACCOUNT_COMPRESSION_NOT_ALLOWED` (-43) - Account compression is not allowed
- `TN_VM_ERR_SYSCALL_ACCOUNT_UNCOMPRESSABLE` (-45) - Account cannot be compressed
- `TN_VM_ERR_SYSCALL_INVALID_PROOF_LEN` (-32) - Proof size mismatch
- `TN_VM_ERR_SYSCALL_INVALID_PROOF_SLOT` (-33) - Proof references invalid block slot
- `TN_VM_ERR_SYSCALL_INVALID_STATE_PROOF` (-23) - State proof verification failed
- `TN_VM_ERR_SYSCALL_STATE_BYTES_REMOVED_OVERFLOW` (-48) - State bytes counter overflow during deactivation
- `TN_VM_ERR_SYSCALL_PROGRAM_IN_CALL_STACK` (-49) - Cannot compress a program that is currently executing

## Resource Consumption

### Compute Units

- **Base cost**: `TN_VM_SYSCALL_BASE_COST` (512 units)
- **Proof cost**: Additional units equal to proof size in bytes
- **Data cost**: Additional units equal to account data size in bytes
- **Metadata cost**: Additional units equal to `sizeof(tsdk_account_meta_t)`
- **Total formula**: `base_cost + proof_sz + account_data_sz + sizeof(tsdk_account_meta_t)`

### Memory Pages

- **Page usage**: No immediate page deallocation (compression is logical)
- **Proof storage**: Temporary memory for proof verification
- **Metadata impact**: Account metadata becomes writable if not already

### State Counter Impact

- **GDSC (Global Deactivated State Counter)**: Incremented by `TSDK_ACCOUNT_META_FOOTPRINT + account_data_sz` bytes
- **Purpose**: Tracks deactivated state for the account compression in the global state counter
- **Overflow protection**: Returns `TN_VM_ERR_SYSCALL_STATE_BYTES_REMOVED_OVERFLOW` if counter would overflow
- **GASC/GDSC check**: Compression may be denied if state counter conditions are not met (unless owner/fee payer is compressing)

## Side Effects

- **Account state**: Sets COMPRESSED flag and updates state counter
- **Transaction state**: Records compression proof for transaction
- **Special handling**: Ephemeral and deleted accounts are deleted instead

## Special Cases

**Ephemeral Accounts:**

Ephemeral accounts are simply deleted when “compressed” - they cannot be truly compressed since they don’t persist beyond the transaction.

**Deleted Accounts:**

Accounts that are marked as deleted are removed entirely rather than compressed.

**New Accounts:**

New accounts require a creation-type state proof, while existing accounts require an existing-type proof.

**Program Accounts:**

Program accounts that are currently in the call stack cannot be compressed. This includes the currently executing program and any program that has called into the current execution context. This prevents a program from compressing itself or its callers during execution.

## State Proof Requirements

- **New accounts**: Must use `TN_STATE_PROOF_TYPE_CREATION` proof type
- **Existing accounts**: Must use `TN_STATE_PROOF_TYPE_EXISTING` proof type
- **Proof verification**: Must reference valid block slot and verify against state root
- **Account hash**: Proof must match the computed hash of the account’s current state

## Transaction Limitations

- Only one account can be compressed per transaction
- The transaction records the compression proof and account details
- Compression state is tracked to prevent multiple compressions

## Usage Notes

- Account must be writable in the transaction (signer approval)
- State proof ensures the account state is correctly recorded
- Compressed accounts can later be decompressed with valid proofs
- The account’s state counter is updated to the proof block’s counter
- Program accounts cannot be compressed while they are in the call stack (current program or any caller)

## Example

```c
#include <thru-sdk/c/tn_sdk_syscall.h>

// Compress an account with state proof
ulong account_idx = 2;
uchar proof_data[2048];
ulong proof_size = prepare_compression_proof(account_idx, proof_data);

ulong result = tsys_account_compress(account_idx, proof_data, proof_size);

if (result == TN_VM_SYSCALL_SUCCESS) {
    // Account compressed successfully
    // COMPRESSED flag set
    // State counter updated
    // Compression proof recorded in transaction
}
```