> ## Documentation Index
> Fetch the complete documentation index at: https://developer.box.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Upload Part
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When you want to upload a large file,
you can split it into smaller parts and
upload them using the Upload Part API.
## Create Upload Session
First, create an upload session. The resulting
object defines the size of each part and the number of parts to upload.
```json theme={null}
{
"id": "F971964745A5CD0C001BBE4E58196BFD",
"type": "upload_session",
"session_expires_at": "2012-12-12T10:53:43-08:00",
"part_size": 1024,
"total_parts": 1000,
"num_parts_processed": 455,
"session_endpoints": {
"upload_part": "https://upload.box.com/api/2.0/files/upload_sessions/F971964745A5CD0C001BBE4E58196BFD",
"commit": "https://upload.box.com/api/2.0/files/upload_sessions/F971964745A5CD0C001BBE4E58196BFD/commit",
"abort": "https://upload.box.com/api/2.0/files/upload_sessions/F971964745A5CD0C001BBE4E58196BFD",
"list_parts": "https://upload.box.com/api/2.0/files/upload_sessions/F971964745A5CD0C001BBE4E58196BFD/parts",
"status": "https://upload.box.com/api/2.0/files/upload_sessions/F971964745A5CD0C001BBE4E58196BFD",
"log_event": "https://upload.box.com/api/2.0/files/upload_sessions/F971964745A5CD0C001BBE4E58196BFD/log"
}
}
```
## Split File
Split the file into parts to be uploaded.
If you want to use the command line,
use the `split` command:
```bash theme={null}
split -b
```
For example:
```bash theme={null}
split -b 8388608 video.mp3 videopart
```
This will result in your file divided into several files.
## Get SHA Digest
To get the value for the `SHA` digest,
use the following openSSL command
to encode the file part:
```bash theme={null}
openssl sha1 -binary | base64
```
For example:
```bash theme={null}
openssl sha1 -binary videoparta | base64
```
The result is a base-64 encoded message used to verify the upload.
## Upload Part
Upload the bytes for the part you want to upload, specifying the byte
range for the part and the `SHA` digest to ensure the content is
uploaded correctly.
```sh cURL theme={null}
curl -i -X PUT "https://upload.box.com/2.0/files/upload_sessions/F971964745A5CD0C001BBE4E58196BFD" \
-H "authorization: Bearer " \
-H "digest: sha=fpRyg5eVQletdZqEKaFlqwBXJzM=" \
-H "content-range: bytes 8388608-16777215/445856194" \
-H "content-type: application/octet-stream" \
--data-binary @
```
```typescript Node/TypeScript v10 theme={null}
await client.chunkedUploads.uploadFilePart(
acc.uploadSessionId,
generateByteStreamFromBuffer(chunkBuffer),
{
digest: digest,
contentRange: contentRange,
} satisfies UploadFilePartHeadersInput,
);
```
```python Python v10 theme={null}
client.chunked_uploads.upload_file_part(
acc.upload_session_id,
generate_byte_stream_from_buffer(chunk_buffer),
digest,
content_range,
)
```
```cs .NET v10 theme={null}
await client.ChunkedUploads.UploadFilePartAsync(uploadSessionId: acc.UploadSessionId, requestBody: Utils.GenerateByteStreamFromBuffer(buffer: chunkBuffer), headers: new UploadFilePartHeaders(digest: digest, contentRange: contentRange));
```
```swift Swift v10 theme={null}
try await client.chunkedUploads.uploadFilePart(uploadSessionId: acc.uploadSessionId, requestBody: Utils.generateByteStreamFromBuffer(buffer: chunkBuffer), headers: UploadFilePartHeaders(digest: digest, contentRange: contentRange))
```
```java Java v10 theme={null}
client.getChunkedUploads().uploadFilePart(acc.getUploadSessionId(), generateByteStreamFromBuffer(chunkBuffer), new UploadFilePartHeaders(digest, contentRange))
```
```java Java v5 theme={null}
//Reading a large file
FileInputStream fis = new FileInputStream("My_Large_File.txt");
//Create the digest input stream to calculate the digest for the whole file.
DigestInputStream dis = new DigestInputStream(fis, digest);
List parts = new ArrayList();
//Get the part size. Each uploaded part should match the part size returned as part of the upload session.
//The last part of the file can be less than part size if the remaining bytes of the last part is less than
//the given part size
long partSize = sessionInfo.getPartSize();
//Start byte of the part
long offset = 0;
//Overall of bytes processed so far
long processed = 0;
while (processed < fileSize) {
long diff = fileSize - processed;
//The size last part of the file can be less than the part size.
if (diff < partSize) {
partSize = diff;
}
//Upload a part. It can be uploaded asynchorously
BoxFileUploadSessionPart part = session.uploadPart(dis, offset, (int)partSize, fileSize);
parts.add(part);
//Increase the offset and proceesed bytes to calculate the Content-Range header.
processed += partSize;
offset += partSize;
}
```
```python Python v4 theme={null}
upload_session = client.upload_session('11493C07ED3EABB6E59874D3A1EF3581')
offset = upload_session.part_size * 3
total_size = 26000000
part_bytes = b'abcdefgh'
part = upload_session.upload_part_bytes(part_bytes, offset, total_size)
print(f'Successfully uploaded part ID {part["part_id"]}')
```
```javascript Node v4 theme={null}
// Upload the part starting at byte offset 8388608 to upload session '93D9A837B45F' with part ID 'feedbeef'
client.files.uploadPart('93D9A837B45F', part, 8388608, 2147483648, {part_id: 'feedbeef'}, callback);
```
### Content Range
Each part’s size must be exactly equal in size to the part size
specified in the upload session that you created.
One exception is the last part of the file, as
this can be smaller. The `Content-Range` parameter
definition follows this pattern:
```yaml theme={null}
-H "Content-Range: bytes -/"
```
When providing the value for `Content-Range`, remember that:
* The lower bound of each part's byte range must be a multiple of the part size.
* The higher bound must be a multiple of the part size - 1.
For example, if the part size is `8388608`,
the content range for the first two parts will be:
```yaml theme={null}
-H "Content-Range: bytes 0-8388607/32127641" \ ## first part
-H "Content-Range: bytes 8388608-16777215/32127641" \ ## second part
```
## Response
After each upload, the resulting response includes
the `ID` and `SHA` of the part uploaded.
```json theme={null}
{
"part_id": "6F2D3486",
"offset": 16777216,
"size": 3222784,
"sha1": "134b65991ed521fcfe4724b7d814ab8ded5185dc"
}
```
Keep all the JSON responses from all part
uploads as they are needed to commit the session.
## Range Overlap
If a part upload request fails with any error code
`range_overlaps_existing_part` then the application
made a mistake in cutting up the file into parts
and tried to upload a part into a range that already had
content uploaded for it. The application should assume
that this last part was not persisted to the session.
## Parallel uploads
Although you can upload the parts in parallel, try to upload them in
order as much as is possible. Parts with a lower byte offset should be uploaded
before parts with a higher byte offset.
The recommended approach is to upload 3 to 5 parts in parallel from a queue
of parts, ordered by byte offset. If a part upload fails, retry it
before you upload further parts.