1# Files API — Go
2 
3## Files API (Beta)
4 
5Under `client.Beta.Files`. Method is **`Upload`** (NOT `New`/`Create`), params struct is `BetaFileUploadParams`. The `File` field takes an `io.Reader`; use `anthropic.File()` to attach a filename + content-type for the multipart encoding.
6 
7```go
8f, _ := os.Open("./upload_me.txt")
9defer f.Close()
10 
11meta, err := client.Beta.Files.Upload(ctx, anthropic.BetaFileUploadParams{
12    File:  anthropic.File(f, "upload_me.txt", "text/plain"),
13    Betas: []anthropic.AnthropicBeta{anthropic.AnthropicBetaFilesAPI2025_04_14},
14})
15// meta.ID is the file_id to reference in subsequent message requests
16```
17 
18Other `Beta.Files` methods: `List`, `Delete`, `Download`, `GetMetadata`.
19 
20---
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