Fix Plotly Chart Width Warning In Streamlit

Dec 21, 2025 by Alex Johnson 44 views

Navigating the "kwargs deprecation warning" in Streamlit's Plotly Charts

Hey there, fellow data enthusiasts! Ever found yourself happily crafting a beautiful interactive chart with Streamlit and Plotly, only to be met with a cryptic "kwargs deprecation warning"? You're not alone! It seems like a bit of a head-scratcher, especially when you're just trying to set the width of your chart, a perfectly documented and straightforward parameter. Let's dive into why this might be happening and how we can get around it, ensuring your Streamlit apps run as smoothly as your visualizations are stunning.

The Curious Case of the `kwargs` Warning

So, you've got your plotly_chart function in Streamlit, and you decide to get a bit fancy by setting the width to something like "content". This is a great way to make your charts dynamically adjust to the available space in your app, which is super handy for responsive design. However, instead of a seamless experience, you might see a warning popping up: Variable keyword arguments for st.plotly_chart have been deprecated and will be removed in a future release. Use the config argument instead to specify Plotly configuration options. This warning is a bit misleading because, in this scenario, you're not actually using variable keyword arguments (kwargs) in the way the warning suggests. You're using a clearly documented parameter, width, which is causing this unexpected alert. It's like getting a warning for speeding when you were just cruising along nicely! This issue seems to have crept in after some updates aimed at cleaning up how Plotly configurations are handled within Streamlit, but it's inadvertently flagging legitimate uses of the width and height arguments.

Why is this Happening?

Streamlit, in its continuous effort to improve and streamline its features, has been refining how it handles parameters passed to underlying libraries like Plotly. The core of the issue lies in how Streamlit checks for and processes keyword arguments. It appears that the width and height arguments, when passed directly to st.plotly_chart, are being caught by a general check that looks for any unrecognized keyword arguments. Even though width and height are intended to control the chart's dimensions within the Streamlit layout, the internal logic might be interpreting them as generic kwargs that should be passed to Plotly's configuration rather than being handled by Streamlit itself. This is particularly noticeable when you use string values like "content" or "auto" for these parameters, as these might not align with the expected numerical pixel values that Plotly's internal configuration might anticipate. The developers intended to deprecate the direct passing of Plotly-specific keyword arguments that should instead go into the config dictionary. However, the width and height parameters for controlling the Streamlit container size of the chart seem to be caught in this net, leading to the warning.

The `width='content'` Scenario

Let's look at the provided reproducible example:

import plotly.graph_objects as go
import streamlit as st

fig = go.Figure()
fig.add_trace(go.Barpolar(r=[1], theta=[0], width=[120]))
fig.update_layout(width=500, height=360)

st.plotly_chart(fig, width="content")

In this code, we create a simple Plotly figure and then display it using st.plotly_chart. The crucial part is width="content". This tells Streamlit to adjust the chart's width to fit its container. The fig.update_layout(width=500, height=360) lines are setting the internal dimensions of the Plotly figure itself, which is a separate concern from how Streamlit displays that figure. The warning arises because Streamlit's plotly_chart function has a check for kwargs. When width="content" is passed, it seems to trigger this check, even though width is a recognized parameter by st.plotly_chart for layout purposes. The warning message about "Variable keyword arguments" and directing users to the config argument suggests that Streamlit is trying to differentiate between arguments meant for Streamlit's display logic and those meant for Plotly's internal configuration. Unfortunately, width and height for container sizing are getting misclassified in this process.

Understanding the `config` Argument

The warning message explicitly mentions using the config argument. This is a dictionary that you can pass to st.plotly_chart to control various aspects of the Plotly chart's behavior and appearance, particularly those that are not directly managed by Streamlit's layout. Think of it as a way to pass Plotly-specific settings that don't affect the overall Streamlit app's structure.

What Goes into `config`?

The config dictionary is where you'd put settings related to Plotly's interactivity, tooltips, modebar, and other Plotly-specific options. For example, you might want to disable the zoom or pan controls, customize the hover information, or change the visibility of certain buttons in the Plotly modebar.

Here's a quick example of how you might use the config argument:

import plotly.graph_objects as go
import streamlit as st

fig = go.Figure(
    data=go.Bar(
        x=['A', 'B', 'C'],
        y=[10, 12, 6]
    )
)

# Plotly-specific configuration options
plotly_config = {
    "displaylogo": False,
    "modeBarButtonsToRemove": ["zoom2d", "pan2d", "lasso2d", "zoomIn2d", "zoomOut2d", "autoScale2d", "resetScale2d"]
}

st.plotly_chart(fig, config=plotly_config)

In this snippet, plotly_config is a dictionary containing settings that control Plotly's behavior, like hiding the Plotly logo and removing specific tools from the modebar. This is the intended way to pass these kinds of options.

The Distinction: Streamlit vs. Plotly Arguments

The key takeaway here is understanding the difference between arguments that Streamlit's st.plotly_chart uses for controlling the embedding and layout of the chart within your app, and arguments that are meant to be passed directly to Plotly for internal configuration.

Streamlit Layout Arguments: These include parameters like width, height, use_container_width, and sharing. These arguments tell Streamlit how to display the chart on the page. For example, use_container_width=True (or width='auto', width='content') makes the chart span the width of its parent container.
Plotly Configuration Arguments: These are arguments that are passed down to Plotly's JavaScript configuration. Historically, some of these might have been passed directly as keyword arguments to st.plotly_chart, leading to confusion. The config dictionary is the modern and recommended way to handle these.

The deprecation warning is essentially Streamlit's way of saying, "Hey, if you want to tweak how Plotly itself behaves, use the config dictionary. If you want to control how I display the chart, use arguments like width and height." The bug is that the width argument for layout is being misinterpreted as a Plotly configuration kwarg.

The Regression and Expected Behavior

This issue is indeed a regression, meaning it worked fine in a previous version of Streamlit but is now broken. Users relied on the width and height parameters, especially with values like "content" or "auto", to create responsive and well-fitting visualizations. The expectation is that when you use these documented parameters for layout control, they should function without triggering deprecation warnings for unrelated kwargs. The current behavior, where providing width="content" leads to a kwargs deprecation warning, is not the intended user experience. The fix should involve Streamlit correctly identifying and processing the width and height arguments as layout parameters, distinct from the config dictionary, thus preventing the erroneous warning.

How to Work Around the Warning (for now)

Until a proper fix is implemented in Streamlit, there are a couple of ways you can sidestep this annoying warning:

Explicitly Pass use_container_width=True: While width="content" is often used interchangeably with use_container_width=True, explicitly using the latter can sometimes bypass the specific check that triggers the warning. This is because use_container_width is a boolean flag and might be handled differently internally.
```
import plotly.graph_objects as go
import streamlit as st

fig = go.Figure()
fig.add_trace(go.Barpolar(r=[1], theta=[0], width=[120]))
fig.update_layout(width=500, height=360)

# Use use_container_width instead of width="content"
st.plotly_chart(fig, use_container_width=True)
```
This is often the most direct solution as it uses a parameter specifically designed for this purpose.
Remove the width Argument (if possible): If the exact width control isn't critical for your specific layout, you might be able to simply remove the width="content" (or similar) argument. Streamlit will then default to a reasonable width, and the warning will disappear. This isn't always ideal, but it works if responsiveness isn't the top priority.
Specify Numerical Width/Height: If you need precise control and want to avoid the warning, you can specify a numerical value for width and height in pixels, as Streamlit will likely treat these as valid arguments that don't trigger the kwargs check. However, this sacrifices the dynamic resizing.
```
# Example with numerical width
st.plotly_chart(fig, width=800) # Specify a pixel width
```

While these are workarounds, they highlight the need for a definitive fix from the Streamlit team to ensure that documented and intended parameters function as expected without spurious warnings. The goal is a clean and intuitive experience for developers building amazing data applications.

Debugging Your Streamlit Environment

When encountering issues like this, it's always a good practice to ensure your development environment is up-to-date and configured correctly. The provided debug information gives us valuable clues:

Streamlit version: 1.50.0
Python version: Python 3.14.2
Operating System: MacOs 26.1
Browser: Chrome

These details are crucial for pinpointing the exact context of the bug. Version 1.50.0 is specific, and knowing the Python version and OS helps rule out environment-specific conflicts. If you're running into this, double-checking that you have the latest stable versions of both Streamlit and Plotly installed (pip install --upgrade streamlit plotly) is always a good first step. Sometimes, clearing your browser cache or restarting your Streamlit server can also resolve seemingly persistent issues, though in this case, it appears to be a genuine bug in the Streamlit code itself.

Conclusion: Towards Smoother Streamlit Visualizations

The "kwargs deprecation warning" when using width="content" in st.plotly_chart is a peculiar bug that stems from how Streamlit handles its arguments. While the warning is intended to guide users towards the config dictionary for Plotly-specific settings, it's currently misfiring on layout-related parameters like width. The good news is that it's recognized as a regression, and the Streamlit team is likely working on a solution. In the meantime, using use_container_width=True is a reliable workaround to maintain responsive chart sizing without the warning.

Streamlit is a fantastic tool for building interactive data applications, and addressing these kinds of small but irritating bugs helps make the development process even more enjoyable. Keep experimenting, keep building, and stay tuned for updates that will iron out these kinks!

For more information on Streamlit components and best practices, check out the official Streamlit Documentation. And for deep dives into Plotly's capabilities, the Plotly Documentation is an invaluable resource.