Fixing The Plotly Chart Width Content Deprecation Warning

Dec 18, 2025 by Alex Johnson 60 views

Addressing the Plotly Chart Width `"content"` Deprecation Warning

Hey there, fellow Streamlit enthusiasts! Have you ever been happily building your interactive dashboards, only to be greeted by an unexpected deprecation warning when using st.plotly_chart with the width="content" argument? You're not alone! It seems like even when you're playing by the rules and sticking to documented parameters, Streamlit sometimes throws a little caution our way. Let's dive into this peculiar behavior and figure out what's going on.

The Sneaky `kwargs` Warning

So, you've crafted a beautiful Plotly chart, and you want it to dynamically adjust its width to fit its content within your Streamlit app. You remember seeing the documentation suggest width="content" as a neat way to achieve this. You add it to your st.plotly_chart call, expecting everything to be smooth sailing. But then, bam! A deprecation warning pops up, something along the lines of: "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 is quite perplexing, especially when you haven't explicitly passed any "variable" keyword arguments. You were just using width="content", which seems like a perfectly legitimate, documented parameter. It feels a bit like being told off for speaking when you were only whispering the correct words. This warning, while intended to guide users towards a more robust configuration method, is inadvertently flagging perfectly valid usage. It's a classic case of a helpful feature causing a bit of confusion. The underlying issue seems to stem from how Streamlit handles arguments passed to st.plotly_chart. It appears that even when you're not using arbitrary **kwargs, the internal mechanisms for handling parameters like width might be triggering a check that looks for unused keyword arguments, leading to this warning. This isn't a bug in your code, but rather a nuance in how the Streamlit component is interpreting the arguments it receives. It’s important to understand that st.plotly_chart is a wrapper around Plotly's extensive charting capabilities, and Streamlit itself manages the rendering and interaction. When you provide arguments like width or height, Streamlit's backend processes these to ensure the chart is displayed correctly within the app's layout. The deprecation warning is specifically about the way extra or unrecognized keyword arguments are handled. In this scenario, the width="content" argument, while valid for controlling the chart's display, might be internally processed in a way that resembles the passing of a keyword argument that the st.plotly_chart function itself doesn't directly recognize as a top-level parameter for its own signature, but rather expects to be part of the Plotly config object. This can lead to the warning being triggered even when the argument is functionally correct and intended for chart sizing. It’s a subtle distinction, but crucial for understanding why the warning appears. The Streamlit team is likely working on refining how these arguments are parsed to avoid such false positives, ensuring that documented and intended parameters don't trigger deprecation notices meant for unintended usage.

Reproducing the Issue: A Simple Example

To make sure we're all on the same page, let's look at a straightforward code example that reliably produces this warning. It’s a minimal setup that highlights the problem without any unnecessary complexity.

import plotly.graph_objects as go
import streamlit as st

# Create a basic Plotly figure
fig = go.Figure()
fig.add_trace(go.Barpolar(r=[1], theta=[0], width=[120]))

# Set some layout properties for the figure
fig.update_layout(width=500, height=360)

# Display the chart with width="content"
st.plotly_chart(fig, width="content")

When you run this simple script in your Streamlit environment (with version 1.50.0 or similar), you'll see the Plotly chart rendered, but you'll also be greeted with that familiar deprecation warning. This happens because, internally, Streamlit's st.plotly_chart function might be processing the width="content" argument in a way that it interprets as an unrecognized keyword argument, even though it's a valid parameter for controlling the output's width. The warning is specifically designed to catch the use of **kwargs that aren't explicitly handled by the st.plotly_chart function itself. The goal is to push users towards using the config dictionary for more advanced Plotly-specific settings. However, in this case, width="content" is a Streamlit-level argument for controlling the display of the chart component, not a Plotly trace or layout attribute passed directly. The warning seems to be triggered because the argument, while valid for Streamlit's plotly_chart function, is being flagged by the internal check that looks for any extra keyword arguments. It's a bit like a security guard seeing someone pass a valid ID but still asking to see the ID because they're looking for anyone without an ID. The intention behind the warning is excellent – to prevent misuse of keyword arguments and encourage structured configuration. But in this specific instance, it's catching a valid use case. This makes the warning appear unnecessarily. The solution likely lies in refining the argument parsing within st.plotly_chart to differentiate between Streamlit-specific display arguments and general Plotly configuration options that should indeed be passed via the config dictionary. For now, this reproducible example serves to pinpoint the exact behavior we're discussing.

Understanding the Expected vs. Current Behavior

Let's clarify what we anticipate versus what we're actually observing. This distinction is key to understanding the problem and its potential solutions.

Expected Behavior

Our ideal scenario is straightforward. When we transition from older methods, like the deprecated use_container_width, to the current recommended width argument, we expect a clean experience. Specifically, using width="content" (or width=some_pixel_value) should not trigger any deprecation warnings related to keyword arguments. The documentation guides us to use these parameters for controlling the chart's dimensions, and we expect them to function as described without raising unnecessary alerts. In an ideal world, Streamlit's plotly_chart function would recognize width as a first-class argument for controlling the component's display and would not confuse it with arbitrary, unhandled kwargs. This means that passing width="content" or width=500 should be treated as a valid and documented instruction, and no warning should be issued. The warning is intended for situations where a user might try to pass, for example, st.plotly_chart(fig, title="My Chart"), where title is a Plotly layout argument that should instead be within the fig.update_layout() call or the config dictionary. By not triggering the warning for width, Streamlit would provide a more intuitive and less confusing user experience, allowing developers to focus on building their applications rather than troubleshooting misleading warnings. This aligns with the general principle of clear and predictable API behavior.

Current Behavior

As we've seen, the reality is a bit different. When you use st.plotly_chart(fig, width="content"), you receive a deprecation warning: "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 appears because, in recent versions of Streamlit (like 1.50.0), there's a check for kwargs within the st.plotly_chart function. If any kwargs are present that aren't explicitly part of the function's signature, this warning is triggered. The issue is that width="content" is being caught by this kwargs check, even though it's a documented and intended way to control the chart's display. The code snippet that seems to be causing this is:

if kwargs:
 show_deprecation_warning(
 "Variable keyword arguments for st.plotly_chart have been "
 "deprecated and will be removed in a future version. Use the "
 "config argument instead to specify Plotly configuration "
 "options."
 )

This block of code executes when kwargs is not empty. Since width="content" is passed as a keyword argument, and it might not be directly processed by the st.plotly_chart function itself before being passed down, it ends up in the kwargs collection, triggering the warning. This is particularly confusing because the width parameter is a documented parameter of st.plotly_chart for controlling the component's width, distinct from Plotly's internal layout.width. The warning is meant for passing arbitrary Plotly settings that should go into the config dict, not for Streamlit's own display arguments. This behavior is a regression because, in previous versions, using width="content" did not produce this warning.

Is This a Regression?

Yes, this appears to be a regression. Based on the behavior described and the expectation that documented parameters should not trigger deprecation warnings meant for unintended usage, the current behavior represents a step backward. Previously, using width="content" in st.plotly_chart worked as expected without raising any deprecation notices. The introduction of stricter kwargs checking, while likely aimed at improving API clarity, has inadvertently created this issue for a valid use case. This is a common challenge in software development: changes intended to improve the system can sometimes have unforeseen consequences on existing functionality. The fact that it used to work correctly and now doesn't strongly indicates a regression.

Debugging Information

To further assist in pinpointing and resolving this issue, here's some relevant debug information:

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

This information should help the development team identify the specific environment and versions where this problem is occurring. It's crucial for developers to have these details to reproduce the issue accurately and test potential fixes effectively.

Conclusion and Next Steps

It's clear that the st.plotly_chart(fig, width="content") call is triggering an unnecessary deprecation warning due to how keyword arguments are being handled internally. While the warning's intention to guide users towards the config dictionary for Plotly-specific settings is commendable, it's misfiring in this instance by flagging a valid Streamlit-specific display parameter. This is a regression that impacts the developer experience.

The Streamlit team is aware of this issue and is likely working on refining the argument parsing in st.plotly_chart to distinguish between Streamlit display arguments and Plotly configuration options. In the meantime, if you encounter this warning, know that your code is likely correct, but the warning is a bit misleading.

For those looking for more context on Streamlit's plotting capabilities and best practices, exploring the official Streamlit documentation on plotting can provide valuable insights into how charts are integrated and managed within Streamlit applications.