Server configuration

The server property can be configured to link to the server API endpoints. Only after these have been configured can FilePond asynchronously upload files to a server.

We'll first go over the different end points and what they do before discussing how to configure them. The advanced section covers how to use functions to fully change how FilePond interacts with the server.

Server end points

Process

Asynchronously uploading files with FilePond is called processing. In short, FilePond sends a file to the server and expects the server to return a unique file id. This unique id is then used to revert uploads or restore earlier uploads.

Along with the file object, FilePond also sends the file metadata to the server, both these objects are given the same name.

The upload process described over time:

  1. FilePond uploads file my-file.jpg as multipart/form-data using a POST request
  2. server saves file to unique location tmp/12345/my-file.jpg
  3. server returns unique location id 12345 in text/plain response
  4. FilePond stores unique id 12345 in a hidden input field
  5. client submits the FilePond parent form containing the hidden input field with the unique id
  6. server uses the unique id to move tmp/12345/my-file.jpg to its final location and remove the tmp/12345 folder

FilePond uses unique file ids to prevent showing information about the server file structure to the client.

Process chunks

To process files in chunks set chunkUploads to true.

FilePond will then slice up files bigger than the set chunkSize into parts. Files smaller than the chunkSize will be posted to the process end point. If you want to force all files to be posted to the chunk end point set chunkForce to true.

Custom headers used in requests

Header Description
Upload-Length The total size of the file being transferred
Upload-Name The name of the file being transferred
Upload-Offset The offset of the chunk being transferred
Content-Type The content type of a patch request, set to 'application/offset+octet-stream'

In short:

In detail:

  1. FilePond requests a transfer id from the server, a unique location to identify this transfer with. It does this using a POST request. The request is accompanied by the metadata and the total file upload size set to the Upload-Length header.
  2. server create unique location tmp/12345/
  3. server returns unique location id 12345 in text/plain response
  4. FilePond stores unique id 12345 in file item
  5. FilePond sends first chunk using a PATCH request adding the unique id 12345 in the URL, each PATCH request is accompanied by a Upload-Offset, Upload-Length, and Upload-Name header. The Upload-Offset header contains the byte offset of the chunk, the Upload-Length header contains the total file size, the Upload-Name header contains the file name.
  6. FilePond sends chunks until all chunks have been uploaded succesfully.
  7. server creates the file if all chunks have been received succesfully.
  8. FilePond stores the unique id 12345 as the server id of this file.
  9. client submits the FilePond parent form containing the hidden input field with the unique id
  10. server uses the unique id to move tmp/12345/my-file.jpg to its final location and remove the tmp/12345 folder

If one of the chunks fails to upload after the set amount of retries in chunkRetryDelays the user has the option to retry the upload.

  1. FilePond As FilePond remembers the previous transfer id the process now starts of with a HEAD request accompanied by the transfer id (12345) in the URL.
  2. server responds with Upload-Offset set to the next expected chunk offset in bytes.
  3. FilePond marks all chunks with lower offsets as complete and continues with uploading the chunk at the requested offset.

Everything continues like normal.

Revert

There's one way the client can deviate from the previous path and that is by reverting the upload. Let's go back to step five and switch to this alternate reality.

  1. FilePond sends DELETE request with 12345 as body by tapping the undo button
  2. server removes temporary folder matching the supplied id tmp/12345 and returns an empty response

This is another reason why FilePond uses unique ids. If we're going to give the client the power to influence the server file system that power should be very minimal.

Restore

FilePond uses the restore end point to restore temporary server files. This might be useful in a situation where the user closes the browser window but hadn't finished completing the form. Temporary files can be set with the files property.

Step one and two now look like this.

  1. FilePond requests restore of file with id 12345 using a GET request
  2. server returns a file object with header Content-Disposition: inline; filename="my-file.jpg"

Load

The restore end point is used to restore a temporary file, the load end point is used to restore already uploaded server files. These files might be located in a database or somewhere on the server file system. Either way they might not be directly accessible from the web.

For situations where a user might want to edit an existing file selection we can use the load end point to restore those files.

  1. FilePond requests restore of file with id 12345 or a file name using a GET request
  2. server returns a file object with header Content-Disposition: inline; filename="my-file.jpg"

Fetch

The fetch end point is used to load files located on remote servers. When a user drops a remote link, FilePond asks the server to download it (CORS might otherwise block it). In this situation the server serves as a proxy.

  1. FilePond requests fetch of file http://somewhere/their-file.jpg using a GET request
  2. server returns a file object as if the file is located on the server

An alternative is to configure FilePond to only do a HEAD request. The server should then save the file to tmp/12345/my-file.jpg and return response headers with the required file information.

header('Access-Control-Expose-Headers: Content-Disposition, Content-Length, X-Content-Transfer-Id');
header('Content-Type: image/jpeg');
header('Content-Length: 3965123');
header('Content-Disposition: inline; filename="my-file.jpg"');
header('X-Content-Transfer-Id: 12345');

Remove

The remove end point is used to remove local files located on the server. This end point is not enabled by default and can only be set to a custom function.

Configuration

The server configuration property expects an object or a URL. If it's not defined, FilePond will not be able to upload file to the server or use fetch functionality.

URL

Setting a single URL is the most basic form of defining a server configuration.

FilePond.setOptions({
    server: './',
});

This tells FilePond the api is located at the same location as the current page. It will then assume it can call all methods on this url. Like shown below.

Method Type Path
process POST
revert DELETE
load GET ?load=<source>
restore GET ?restore=<id>
fetch GET | HEAD ?fetch=<url>
patch PATCH ?patch=<id>

We can of course supply a path or URL to another location, FilePond will simply append the above default paths to the supplied value. If we want more fine grained control we can use an object to configure the server end points.

Object Configuration

To setup asynchronous uploading only, we pass the location of the process end point.

FilePond.setOptions({
    server: {
        process: './process',
        fetch: null,
        revert: null,
    },
});

This configuration assumes that the process end point is located on the same server. Reverting a file upload and fetching a remote file have been disabled. Restoring or loading an earlier uploaded file with this configuration is also not possible.

To unlock these features we have to supply FilePond with some more end points using the revert, fetch, load and restore properties.

FilePond.setOptions({
    server: {
        process: './process',
        revert: './revert',
        restore: './restore/',
        load: './load/',
        fetch: './fetch/',
    },
});

FilePond will append the dropped URL to the fetch method, and the unique file id will automatically be added to the restore and load end points. restore, load and fetch are GET requests while process is a POST request and revert is a DELETE request.

If the endpoints are located on a different server we can add a url property to tell FilePond its location.

FilePond.setOptions({
server:{
    url: 'http://192.168.0.100',
    process: './process',
    revert: './revert',
    restore: './restore/',
    load: './load/',
    fetch: './fetch/'
});

Depending on our project we might have to pass additional information to each request. We can accomplish this by turning the end point into an object which allows for more fine grain control over how FilePond handles each request.

For brevity we'll only look at the process property. All other properties can be configured with the same configuration object.

FilePond.setOptions({
    server: {
        url: 'http://192.168.0.100',
        process: {
            url: './process',
            method: 'POST',
            withCredentials: false,
            headers: {},
            timeout: 7000,
            onload: null,
            onerror: null,
            ondata: null,
        },
    },
});
Property Description Required
url Path to the end point yes
method Request method to use no
withCredentials Toggles the XMLHttpRequest withCredentials on or off no
headers An object containing additional headers to send, or when uploading chunks this can be a function that is expected to return a header object no
timeout Timeout for this action no
onload Called when server response is received, useful for getting the unique file id from the server response no
onerror Called when server error is received, receives the response body, useful to select the relevant error data no
ondata Called with the formdata object right before it is sent, return extended formdata object to make changes no

A more elaborate server configuration is shown below. This configuration reveals the timeout property as assigned to the server object. This sets it for all end points, it can also be configured per end point.

FilePond.setOptions({
    server: {
        url: 'http://192.168.0.100',
        timeout: 7000,
        process: {
            url: './process',
            method: 'POST',
            headers: {
                'x-customheader': 'Hello World',
            },
            withCredentials: false,
            onload: (response) => response.key,
            onerror: (response) => response.data,
            ondata: (formData) => {
                formData.append('Hello', 'World');
                return formData;
            },
        },
        revert: './revert',
        restore: './restore/',
        load: './load/',
        fetch: './fetch/',
    },
});

If we want to disable certain end points we can pass a null instead of string or object. Say we only want to use the fetch functionality and not do asynchronous uploading we can disable processing. In that situation revert and restore do not make a lot of sense (since we're no longer uploading temporary files) so we can remove those.

FilePond.setOptions({
    server: {
        url: 'http://192.168.0.100',
        timeout: 7000,
        process: null,
        load: './load/',
        fetch: './fetch/',
    },
});

Advanced

If we require even more control we can configure each end point as a function instead of an object. FilePond will then run our function and supply callback methods to control the FilePond interface.

Note that in the examples below we make use of arrow functions, these can of course also be written as a classic function.

Process

The custom process function receives a file object plus a set of FilePond callback methods to return control to FilePond. The file parameter contains the native file object (instead of a FilePond file item) access the file item is restricted in the process function to prevent setting properties or running functions that would would contradict or interfere with the current processing of the file.

The transfer and options parameters are only to be used when uploading chunks. Use transfer to return the transfer id to FilePond, the options parameter contains the chunk related options.

FilePond.setOptions({
    server: {
        process: (fieldName, file, metadata, load, error, progress, abort, transfer, options) => {
            // fieldName is the name of the input field
            // file is the actual file object to send
            const formData = new FormData();
            formData.append(fieldName, file, file.name);

            const request = new XMLHttpRequest();
            request.open('POST', 'url-to-api');

            // Should call the progress method to update the progress to 100% before calling load
            // Setting computable to false switches the loading indicator to infinite mode
            request.upload.onprogress = (e) => {
                progress(e.lengthComputable, e.loaded, e.total);
            };

            // Should call the load method when done and pass the returned server file id
            // this server file id is then used later on when reverting or restoring a file
            // so your server knows which file to return without exposing that info to the client
            request.onload = function () {
                if (request.status >= 200 && request.status < 300) {
                    // the load method accepts either a string (id) or an object
                    load(request.responseText);
                } else {
                    // Can call the error method if something is wrong, should exit after
                    error('oh no');
                }
            };

            request.send(formData);

            // Should expose an abort method so the request can be cancelled
            return {
                abort: () => {
                    // This function is entered if the user has tapped the cancel button
                    request.abort();

                    // Let FilePond know the request has been cancelled
                    abort();
                },
            };
        },
    },
});

Revert

Custom revert methods receive the unique server file id and a load and error callback.

FilePond.setOptions({
    server: {
        revert: (uniqueFileId, load, error) => {
            // Should remove the earlier created temp file here
            // ...

            // Can call the error method if something is wrong, should exit after
            error('oh my goodness');

            // Should call the load method when done, no parameters required
            load();
        },
    },
});

Load

Custom load methods receive the local file source, and the callback methods: load, error, abort, and headers.

FilePond.setOptions({
    server: {
        load: (source, load, error, progress, abort, headers) => {
            // Should request a file object from the server here
            // ...

            // Can call the error method if something is wrong, should exit after
            error('oh my goodness');

            // Can call the header method to supply FilePond with early response header string
            // https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/getAllResponseHeaders
            headers(headersString);

            // Should call the progress method to update the progress to 100% before calling load
            // (endlessMode, loadedSize, totalSize)
            progress(true, 0, 1024);

            // Should call the load method with a file object or blob when done
            load(file);

            // Should expose an abort method so the request can be cancelled
            return {
                abort: () => {
                    // User tapped cancel, abort our ongoing actions here

                    // Let FilePond know the request has been cancelled
                    abort();
                },
            };
        },
    },
});

Fetch

The custom fetch method receives the url to fetch and a set of FilePond callback methods to return control to FilePond.

FilePond.setOptions({
    server: {
        fetch: (url, load, error, progress, abort, headers) => {
            // Should get a file object from the URL here
            // ...

            // Can call the error method if something is wrong, should exit after
            error('oh my goodness');

            // Can call the header method to supply FilePond with early response header string
            // https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/getAllResponseHeaders
            headers(headersString);

            // Should call the progress method to update the progress to 100% before calling load
            // (computable, loadedSize, totalSize)
            progress(true, 0, 1024);

            // Should call the load method with a file object when done
            load(file);

            // Should expose an abort method so the request can be cancelled
            return {
                abort: () => {
                    // User tapped abort, cancel our ongoing actions here

                    // Let FilePond know the request has been cancelled
                    abort();
                },
            };
        },
    },
});

Restore

Custom restore methods receive the server file id of the file to restore and a set of FilePond callback methods to return control to FilePond.

FilePond.setOptions({
    server: {
        restore: (uniqueFileId, load, error, progress, abort, headers) => {
            // Should get the temporary file object from the server
            // ...

            // Can call the error method if something is wrong, should exit after
            error('oh my goodness');

            // Can call the header method to supply FilePond with early response header string
            // https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/getAllResponseHeaders
            headers(headersString);

            // Should call the progress method to update the progress to 100% before calling load
            // (computable, loadedSize, totalSize)
            progress(true, 0, 1024);

            // Should call the load method with a file object when done
            load(serverFileObject);

            // Should expose an abort method so the request can be cancelled
            return {
                abort: () => {
                    // User tapped abort, cancel our ongoing actions here

                    // Let FilePond know the request has been cancelled
                    abort();
                }
            };
        };
    }
});

Remove

The custom remove method receives the local file source and a load and error callback.

This method is null by default as giving clients the power to remove files from the server in this way might not be very secure. But, because of popular demand the method has been added.

FilePond.setOptions({
    server: {
        remove: (source, load, error) => {
            // Should somehow send `source` to server so server can remove the file with this source

            // Can call the error method if something is wrong, should exit after
            error('oh my goodness');

            // Should call the load method when done, no parameters required
            load();
        },
    },
});