> ## Documentation Index > Fetch the complete documentation index at: https://docs.abbyy.com/llms.txt > Use this file to discover all available pages before exploring further. # Working with files > Exchange files with the ABBYY FlexiCapture Application Server using POST requests: load, save, append, and checksum images, attachments, and XML data. To exchange files with the Application Server, use a POST request. Before you send file requests, connect to the Web Services API. For more information, see [Connecting to the Web Services API](/flexi-capture/api/using/connecting). ## Types of actions Use POST requests to perform the following actions: | Action value | Description | | ------------ | --------------------------------------------------------------------------------------------- | | `Load` | Load files from the server. | | `Save` | Save files on the server. | | `Append` | Append data to the end of a file. | | `Checksum` | Get a checksum for a file from the server. The checksum is calculated using the CRC32 method. | ## Common use cases * Import images. Load image files, including in parts, and get their checksum. * Get original page images at any point during processing. * Work with attachments of batches, documents, and pages (upload and download). * Get the XML description of a verification task, modify the document, and save the changes on the server. For large attachments, use POST requests. Large files are divided into smaller parts and uploaded to the server. When you use a POST request to add an attachment to an object, call the [SaveAttachment](/flexi-capture/api/methods/save-attachment) method after the POST request, passing a zero-length file with the name of the transferred file as the `file` parameter. In other cases, use the [Attachments](/flexi-capture/api/methods/attachments) methods developed specifically for attachments. ## Request parameters Make sure that the request fields are completed correctly. | Name | Type | Description | | ------------ | ------ | ------------------------------------------------------------------------------------------------------------- | | `Action` | string | Type of action. For more information, see [Types of actions](#types-of-actions). | | `sessionId` | int | Session ID, used to check the user's permissions. | | `projectId` | int | Project ID. | | `batchId` | int | Batch ID. | | `objectType` | int | Type of object on the server. For more information, see [Object types](#object-types). | | `objectId` | int | Object ID (of a document, page, or task). | | `parentId` | int | ID of the parent document. Specify this for document sets; for documents that are not part of a set, use `0`. | | `version` | int | File version. | | `streamName` | string | Name of the encoded binary stream. For more information, see [Stream names](#stream-names). | | `blob` | — | Binary file data (when `Action` is `Save` or `Append`). | | `offset` | int | Offset from the start of the file after which to append the data (when `Action` is `Append`). | ### Object types The `objectType` parameter accepts the following values: | Value | Object type | | ----- | ------------------------------------------------------------------- | | `0` | Document | | `1` | Page | | `5` | Small copy of the page displayed as a thumbnail (PNG file) | | `8` | Task attachment (XML document) | | `13` | File accessible to all users, such as an End-User License Agreement | Object type `8` (task attachment) is most effective for large attachments. In other cases, use the [Attachments](/flexi-capture/api/methods/attachments) methods developed specifically for attachments. For files of object type `13`, set `projectId` to `0` and `batchId` to `0` — these files do not belong to any project, batch, or tenant. To write a file of this type, the administrator must open a session. To read a file of this type, pass `sessionId=0`; there is no need to open a session. ### Stream names The `streamName` parameter is the name of the binary stream. Use Base64 encoding when saving a file to the server, and UrlEncode encoding when loading a file from the server. The available values depend on the object type. #### Page stream names | Value | Description | | ----------------- | ------------------------------------------------- | | `BlackWhiteImage` | The black-and-white image of the page (PNG file). | | `ColorImage` | The color image of the page (JPG file). | | `Preview` | Page preview image (PNG file). | #### Document stream names | Value | Description | | ----------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `DocumentBody` | An XML document that describes document fields. Created when preparing the task for the Web stations. After verification, the changes in the document are processed. Versions are not supported; set the `version` parameter to `0`. Save the document processing results to this file. | | `Page` `pageID` | `pageID` is the ID of a page returned by the [AddNewPage](/flexi-capture/api/methods/add-new-page) method. Use this stream name to upload a source page image before preprocessing. | | `FileName` | `FileName` is the name of a file specified when creating the document with the [AddNewDocument](/flexi-capture/api/methods/add-new-document) method. Use this stream name to upload a multi-page file with document page images. | | `RecognizedWords` | An XML document that contains recognized words and their coordinates on the page. | #### Task stream names * `Verification` — An XML document that describes a verification task. Created when preparing the task for the Web stations. After verification, the changes in the document are processed. Versions are not supported; set the `version` parameter to `1`. Save the task processing results to this file. * `VerificationRequest` — Corresponds to one of the following requests: * An XML document that contains a request to execute operations within a batch, including document separation and page rearrangement. This type of request is used by the Web Station for rule checks. * An XML document containing a routing request. * An XML document containing a `LineItems` extrapolation request. * An XML document containing a data verification request. ## File storage File Storage contains all files of the project. The file name encodes the object type, object identifier, and stream name in the form `--version`. Page files (`objectType = 1`) contain copies of images, while document files (`objectType = 0`) contain source images. For this reason, you cannot change an image using a POST request with `objectType = 1`. ## Example requests ### Load a file from the server To load a page file (`objectType = 1`) with `id=4`, `streamName=C:\Temp\image.pdf`, and `version=184201843` from the server, use the following POST request: ```text theme={null} 1-4-C:\Temp\image.pdf184201843 ``` ### Save a file on the server To save a document (`objectType = 0`) with `id=4`, `projectId=3`, `batchId=6`, `version=522`, and `streamName=C:\Temp\image.pdf` on the server, use the following POST request: ```csharp theme={null} resp = FileRequest( action: "Save", objectType: 0, projectId: 3, batchId: 6, objectId: 4, version: 522, streamName: "C:\Temp\image.pdf", file: new ByteArrayContent(buffer, 0, readed), clientCredentials: clientCredentials, endpointAddress: endpointAddress); ``` For more information, see [Examples](/flexi-capture/api/files/examples-api-files).