> For the complete documentation index, see [llms.txt](https://azutopia.gitbook.io/azu/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://azutopia.gitbook.io/azu/endpoints/return-different-formats.md).
# Return Different Formats
This guide shows you how to return JSON, HTML, text, and other response formats.
## JSON Response
Return JSON data:
```crystal
struct JsonEndpoint
include Azu::Endpoint(EmptyRequest, Azu::Response::Json)
get "/api/data"
def call
json({
message: "Hello",
timestamp: Time.utc.to_rfc3339
})
end
end
```
### Custom JSON Response
```crystal
struct UserResponse
include Azu::Response
def initialize(@user : User)
end
def render
{
id: @user.id,
name: @user.name,
email: @user.email
}.to_json
end
end
```
## Text Response
Return plain text:
```crystal
struct TextEndpoint
include Azu::Endpoint(EmptyRequest, Azu::Response::Text)
get "/health"
def call
text "OK"
end
end
```
## HTML Response
Return HTML content:
```crystal
struct HtmlEndpoint
include Azu::Endpoint(EmptyRequest, Azu::Response::Html)
get "/page"
def call
html <<-HTML
Page
Hello!
HTML
end
end
```
### Using Templates
```crystal
struct TemplateEndpoint
include Azu::Endpoint(EmptyRequest, Azu::Response::Html)
include Azu::Templates::Renderable
get "/users"
def call
view "users/index.html", {
users: User.all,
title: "User List"
}
end
end
```
## Empty Response
Return no content (204):
```crystal
struct DeleteEndpoint
include Azu::Endpoint(EmptyRequest, Azu::Response::Empty)
delete "/users/:id"
def call
user = User.find(params["id"].to_i64)
user.try(&.delete)
status 204
Azu::Response::Empty.new
end
end
```
## Content Negotiation
Return different formats based on Accept header:
```crystal
struct NegotiatedEndpoint
include Azu::Endpoint(EmptyRequest, Azu::Response)
get "/data"
def call
data = {message: "Hello", value: 42}
case accept_type
when "application/json"
json data
when "text/html"
html "#{data[:message]}: #{data[:value]}
"
when "text/plain"
text "#{data[:message]}: #{data[:value]}"
else
json data # Default to JSON
end
end
private def accept_type
headers["Accept"]?.try(&.split(",").first) || "application/json"
end
end
```
## Setting Headers
Add custom response headers:
```crystal
def call
response.headers["X-Custom-Header"] = "value"
response.headers["Cache-Control"] = "max-age=3600"
json({data: "value"})
end
```
## Redirect Response
Redirect to another URL:
```crystal
def call
redirect_to "/new-location"
# or
redirect_to "/new-location", status: 301 # Permanent redirect
end
```
## File Download
Return a file for download:
```crystal
struct DownloadEndpoint
include Azu::Endpoint(EmptyRequest, Azu::Response)
get "/download/:filename"
def call
filename = params["filename"]
file_path = File.join("files", filename)
if File.exists?(file_path)
response.headers["Content-Type"] = "application/octet-stream"
response.headers["Content-Disposition"] = "attachment; filename=\"#{filename}\""
response.body = File.read(file_path)
else
raise Azu::Response::NotFound.new("/download/#{filename}")
end
end
end
```
## See Also
* [Create an Endpoint](/azu/endpoints/create-endpoint.md)
* [Render HTML Templates](/azu/templates/render-html-templates.md)
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