# How to use Plug.ErrorHandler to handle errors

**URL:** <https://forum.elixirforum.com/t/how-to-use-plug-errorhandler-to-handle-errors/68514>\
**Category:** Questions\
**Tags:** plug-error\
**Created:** [January 4, 2025, 11:28am UTC](https://forum.elixirforum.com/t/how-to-use-plug-errorhandler-to-handle-errors/68514 "2025-01-04T11:28:28Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![mszmurlo](https://forum.elixirforum.com/user_avatar/forum.elixirforum.com/mszmurlo/32/20449_2.png) [@mszmurlo](https://forum.elixirforum.com/u/mszmurlo)\
**Post date:** [January 4, 2025, 11:28am UTC](https://forum.elixirforum.com/t/how-to-use-plug-errorhandler-to-handle-errors/68514/1 "2025-01-04T11:28:28Z")

</div>

Hi.

I’m working on a webapp based only on bandit and plugs only and I’m wondering how to handle errors.

For `404` I can put something like

```elixir
  match _ do
    ErrorController.error_404(conn)
  end

```

at the end of the routes list, but that doesn’t catch all other error, as for example `500`. This morning I saw there was a dedicated plug to handle error, yet the documentation is pretty short… And since then I’m struggling to understand how to use it.

My router looks like this:

```elixir
defmodule MEC.Web.Router do

  @moduledoc false
  use Plug.Router
  use Plug.ErrorHandler

  
  require Logger
  alias MEC.Web.PageController
  alias MEC.Web.ErrorController
  
  plug Plug.Logger
  plug :match
  plug :dispatch
  
  get "/", do: PageController.index(conn)
  get "/test", do: FakeController.index(conn) # NOT DEFINED. To simulate an error 500
  
## match _ do
## ErrorController.error_404(conn)
## end
  
  defp handle_errors(conn, %{kind: kind, reason: reason, stack: _stack}) do
    resp = """
Something went wrong:
  kind=#{inspect(kind)}
  reason=#{inspect(reason)}
  conn=#{inspect(conn, pretty: true)}
"""
    send_resp(conn, conn.status, resp)
  end
  
end

```

Notice that `match _ do` is commented to check how `ErrorHandler` handles `404` errors and the controller `FakeController` is not defined at all to simulate an error `500`.

- for `/`: as it is not an error, all is fine
- for `/test` : I get an error `500` (only seen in `conn.status`) which is OK
- for `/other` which sould be an error `404`, I get a `500` with the reason being ` reason=%FunctionClauseError{module: MEC.Web.Router, function: :do_match, arity: 4, kind: nil, args: nil, clauses: nil}`

This is where I’m stuck. Any hint is welcome

---

<div class="post-metadata">

**Author:** ![Hermanverschooten](https://forum.elixirforum.com/user_avatar/forum.elixirforum.com/hermanverschooten/32/6447_2.png) [@Hermanverschooten](https://forum.elixirforum.com/u/Hermanverschooten)\
**Post date:** [January 7, 2025, 6:55am UTC](https://forum.elixirforum.com/t/how-to-use-plug-errorhandler-to-handle-errors/68514/2 "2025-01-07T06:55:39Z")

</div>

`Plug.Router` does not handle the `404` by default according to the [docs](https://hexdocs.pm/plug/readme.html#plug-router).

> This also means that a catch all `match` block is recommended to be defined as in the example above, otherwise routing fails with a function clause error (as it would in any regular Elixir function).

And this is exactly what you are seeing.