;
};
The Pre-flight check API allows an application to verify that a file will be
accepted by Box before it uploads any bytes. It can both be used for new files,
as well as uploading new versions of existing files.
## Checklist
Preflight checks perform all the same checks as if the file was
actually uploaded including:
* The permission of the application and the user to upload to the folder
* Any file name collisions
* Any file size caps and limits
* Any folder and file name restrictions
* Any folder and account storage quotas
## Check for new file
To perform a check for a new file, call the
`OPTIONS /files/content` API with the same
parameters (except for the binary content) as if uploading an actual file.
```sh cURL theme={null}
curl -i -X OPTIONS "https://api.box.com/2.0/files/content" \
-H "authorization: Bearer " \
-H "content-type: application/json" \
-d '{"name":"Contract.pdf", "parent":{"id":"11446498"}}'
```
```typescript Node/TypeScript v10 theme={null}
await client.uploads.preflightFileUploadCheck({
name: newFileName,
size: 1024 * 1024,
parent: { id: '0' } satisfies PreflightFileUploadCheckRequestBodyParentField,
} satisfies PreflightFileUploadCheckRequestBody);
```
```python Python v10 theme={null}
client.uploads.preflight_file_upload_check(
name=new_file_name, size=1024 * 1024, parent=PreflightFileUploadCheckParent(id="0")
)
```
```cs .NET v10 theme={null}
await client.Uploads.PreflightFileUploadCheckAsync(requestBody: new PreflightFileUploadCheckRequestBody() { Name = newFileName, Size = 1024 * 1024, Parent = new PreflightFileUploadCheckRequestBodyParentField() { Id = "0" } });
```
```java Java v10 theme={null}
client.getUploads().preflightFileUploadCheck(new PreflightFileUploadCheckRequestBody.Builder().name(newFileName).size(1024 * 1024).parent(new PreflightFileUploadCheckRequestBodyParentField.Builder().id("0").build()).build())
```
```java Java v5 theme={null}
String fileName = "My Doc.pdf";
BoxFolder rootFolder = BoxFolder.getRootFolder(api);
try {
folder.canUpload(fileName, 98734576);
// If the file upload would not have succeeded, it will not be attempted
folder.uploadFile(fileContents, fileName);
} catch (BoxAPIException ex) (
)
```
```javascript Node v4 theme={null}
// Verify that uploading a 200MB file named "Preso.ppt" to folder 12345 would succeed
client.files.preflightUploadFile(
'12345',
{
name: 'Preso.ppt',
size: 200000000
},
null,
callback
);
```
## Check for new file version
To perform a check for a new version of a file, call the
`OPTIONS /files/:id/content` API with the same
parameters (except for the binary content) as if uploading an actual file.
```sh cURL theme={null}
curl -i -X OPTIONS "https://api.box.com/2.0/files/12345/content" \
-H "authorization: Bearer " \
-H "content-type: application/json" \
-d '{"name":"Contract.pdf", "parent":{"id":"11446498"}}'
```
```javascript Node v4 theme={null}
// Check if uploading a larger version of this file will succeed
client.files.preflightUploadNewFileVersion('87646', {size: 300000000}, null, callback);
```
## Checks & Chunk Uploads
When performing a chunked upload, performing a preflight check is not
required as creating an Upload Session also performs a
preflight check.
## Response codes
When the API call detects any problems, a HTTP `409 Conflict` status code is
returned with a message to describe the possible conflict. If no problems were
discovered, it returns a HTTP `200 OK` status code and the upload can proceed.
A `200 OK` response does not guarantee that the upload call will actually
succeed. Pre-flight checks have show to reduce failed uploads by over 99%, yet
concurrency issues still come into play when uploading a file.
Highly active folders, common filenames, and accounts near their quota
limits may get a `200 OK` for the preflight check, and then have a real conflict
during the actual upload.
## Response body
In many cases, the preflight check will return valuable data in the API response
when a conflict has been detected. For example, when a name collision has been
detected, the application can use the `SHA-1` that is returned in the error
response to check if the existing file is identical to the one it is trying to
upload.