Parse base64 strings to attachments

I’m using a Coda webhook to upload data to a table and I would like to have a column of attachments. It would be a file type column with 0 or more files per row. It doesn’t look like I can use the webhook to upload files directly, so I’m trying to base64 encode the files and upload them to a text column. I would like to have a formula column that parses the base64 strings to actual attachments when a new row is created. I got it working for images via custom pack formula using this approach: Working with images and files - Coda Pack SDK, but I can’t get it working for other file types. I read somewhere in the Coda docs that attachments can only be displayed in a sync table for now, but I wanted to check if there are any better solutions to this.

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I’m able to return the tmp storage url for a single file using this code, although it doesn’t create a native file attachment:


name: “parse_base64_attachments”,

description: “Convert a list of base64 encoded files to native attachments”,

parameters: [
type: coda.ParameterType.StringArray,
name: “b64_str”,
description: “Data string”
type: coda.ParameterType.StringArray,
name: “file_type”,
description: “File type”

resultType: coda.ValueType.Array,
items: { type: coda.ValueType.String },

execute: async function ([b64_str, file_type], context) {

const result = [] as string[];

for (let i = 0; i < b64_str.length; i++) {

  let buffer = Buffer.from(b64_str[i], "base64");

  let tmp_data_url = await context.temporaryBlobStorage.storeBlob(buffer, file_type[i]);



return result;



When I try to a pass a list of base64 strings and a list of file types, I get an internal error:


Please keep updating - really interested in this solution if you find one

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By passing the base64 strings and the file type strings as lists, I’m able to return a list of the temp storage urls, but it’s still not converting to native attachments.


I got it working for images by changing the pack formula to have result type array with items of string and value type attachment:

resultType: coda.ValueType.Array,
items: {
type: coda.ValueType.String,
codaType: coda.ValueHintType.Attachment
It’s not working for other types of attachments (pdf or docx) yet. For those I get this instead of the file:

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Coda will only ingest files and create attachments if this comes through a Sync Table:

So if you need those to actually be stored as attachments, one workaround would be:

  1. The webhook takes the data and stores it to a cell in some temporary table

  2. The pack exposes a Sync Table that’s set up to read from that table:

    • either the temporary table has a specific hard-coded name and the pack locates it by name,
    • or the sync table is a dynamic sync table where you can either select or insert the URL of that temporary table with the data
    • or you can pass the data through a parameter — but I think this may fail because there could be size limits on parameters and the data may not fit these.
  3. The sync table will read the base64 upload, make a file out of it, put to temporary blob storage, and then return it within a sync table as FileAttachment.


Thanks @Paul_Danyliuk for the guidance. I’m not too familiar with sync tables. Can you point me to the docs for how to use an existing table as a source for a sync table?