> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.mythos.new/features/chat-attachments/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.mythos.new/_mcp/server.

# Chat attachments

> Add visual references, documents, data, or audio files to a prompt.

Attach files when Mythos needs the original reference, data, or document to complete a request.
Open the **+** menu beside the composer and choose **Attach**. You can select images and supported
files together, then explain what you want Mythos to do with them.

A screenshot can show the layout you want. A CSV can supply the records for a catalog. A product
brief can explain the feature you want to build. The attachment provides context; your prompt
provides the task.

## Attach files to a prompt

#### Choose your files

Select **+ → Attach** beside the chat composer, then choose files from your device.

#### Review the attachments

Each selected item appears above the composer. Remove anything you do not want to send.
If a file is rejected, read the message and check its type and size.

#### Explain the task

Say what each file contains, which parts matter, and what result you want. For a visual
reference, distinguish the layout to follow from any content or branding to keep.

#### Send and review

Send the prompt and review the result. Check that imported data, document details, and
visual references were used as intended before continuing.

## Supported files

| Type          | Supported inputs                                                 | Use it for                                          |
| ------------- | ---------------------------------------------------------------- | --------------------------------------------------- |
| Images        | PNG, JPEG, WebP, GIF                                             | Screenshots, mockups, photos, and visual references |
| Documents     | PDF, DOCX                                                        | Requirements, source material, or a brief           |
| Data and text | JSON, CSV, UTF-8 text, including supported text-based code files | Records, copy, examples, or a file to inspect       |
| Audio         | MP3, WAV                                                         | An original audio file for a task that uses it      |

Mythos treats supported images as visual input automatically. You do not need to choose a separate
photo picker. Tell Mythos whether an image is a reference or should appear in the app itself.

Attaching an audio file does not automatically transcribe it. Describe the audio task and connect
any service that task requires. Spreadsheets such as XLSX and archives such as ZIP are not accepted
by the chat attachment picker; export the relevant data as CSV or attach supported individual files.

## Attachment limits

These limits apply to one message:

| Limit                    | Maximum       |
| ------------------------ | ------------- |
| All attachments combined | **15 items**  |
| Images within that total | **10 images** |
| Each image               | **5 MiB**     |
| Each non-image file      | **20 MiB**    |
| Combined attachment size | **20 MiB**    |

An image counts toward both the 15-item total and the 10-image total. A group of individually valid
files can still exceed the combined limit. Remove files, reduce their size, or split the task into
smaller requests.

## Give useful direction

With a screenshot:

```text
Use this screenshot as the layout reference for the pricing page.
Keep our existing colors and copy. Match the spacing and card proportions.
```

With a CSV:

```text
Use products.csv as the starting data for the catalog. Show name, category,
and price. Tell me if any row is missing one of those fields.
```

With a document:

```text
Read this product brief and use Plan mode to outline the reservation flow.
Ask about any missing decisions before building.
```

## When files become part of the app

An attachment belongs to the message you send it with. Plan can use it as context without changing
the project's code. In Build, originals are added to the project only with a successful delivery.

An attachment is not automatically displayed on the published site. Ask Mythos to use it in the app
and say where it should appear. A visual reference can guide a design without becoming a public
asset.

> **Warning**
>
> Review attachments before sending. Do not upload passwords, private keys,
> payment secrets, or personal data that the task does not require.

Inputs attached in chat do not appear in **Files**. That view contains the
[generated files](/features/files-and-artifacts) Mythos creates for you.

## Related

* [Writing good prompts](/prompting/writing-good-prompts) — explain references and constraints.
* [Plan mode](/features/plan-mode) — review an approach before changing the project.

> Learn how to turn an idea into a working app, improve it in Mythos, and publish it when it is ready.