Fix Plotly Chart Deprecation Warning With 'content' Width

Dec 21, 2025 by Alex Johnson 58 views

Understanding the Plotly Chart Width='content' Deprecation Warning in Streamlit

Hey there, data visualization enthusiasts! Have you ever been working on your Streamlit dashboards, trying to get your Plotly charts to perfectly fit the content, only to be greeted by a rather unceremonious deprecation warning? You're not alone! It seems that when you try to use st.plotly_chart with the width="content" (or height="content") argument, a warning pops up about kwargs, even if you're not explicitly passing any variable keyword arguments yourself. This can be a bit confusing, especially when you're just using the documented parameters. Let's dive deep into what's happening here, why it's happening, and how we can navigate this little hiccup to keep our Streamlit apps clean and warning-free. We'll break down the issue, explore the context of these changes, and provide a clear path forward so you can confidently resize your Plotly charts.

The Root of the Warning: A Deeper Look at `kwargs` and Streamlit's Evolution

The core of this issue lies in how Streamlit handles arguments passed to its components, particularly st.plotly_chart. The deprecation warning stems from changes made to how Streamlit manages variable keyword arguments (**kwargs). Previously, st.plotly_chart might have been more lenient in accepting various keyword arguments that were then passed down to the underlying Plotly chart configuration. However, as Streamlit evolves, it's tightening its approach to argument handling to improve clarity, prevent unexpected behavior, and ensure better maintainability. The introduction of a more structured way to pass Plotly-specific configurations, often through a dedicated config argument, is part of this evolution. The warning message itself hints at this: "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 means that Streamlit is moving away from a general **kwargs approach for plotly_chart and encouraging the use of a more specific config dictionary for Plotly settings.

The problem arises when you use width="content" (or height="content"). Even though width and height are documented parameters for st.plotly_chart and not arbitrary kwargs, the internal implementation might still be triggering the kwargs check. This could be because the width and height arguments, when set to "content", are being processed in a way that the warning mechanism interprets as a potential misuse of **kwargs. It's a case of the warning being a bit too broad, flagging a legitimate use case as if it were an unsupported arbitrary keyword argument. This is particularly vexing because it suggests a deviation from the expected behavior, especially after referring to the official documentation which lists width and height as valid parameters.

The Streamlit team is actively working on refining these components. The goal is to make the API cleaner and more predictable. When a component like st.plotly_chart is updated, there's often a period where older ways of passing arguments might still work but trigger warnings, signaling that a change is coming. The width="content" functionality is intended to make charts responsive, automatically adjusting to the available container width, which is a very common and useful feature for dashboard development. The deprecation warning, in this specific instance, seems to be an unintended consequence of broader changes to argument parsing. It's a reminder that even well-documented features can sometimes encounter unexpected edge cases during API refactors. The key takeaway is that Streamlit aims to guide developers towards the most robust and future-proof ways of configuring their applications, and in this case, it's nudging users to be mindful of how arguments are passed, especially those related to Plotly's extensive configuration options.

Reproducing the Issue: A Simple Code Snippet

To truly understand the problem, let's look at the code example provided. It's concise and directly illustrates the scenario. Here’s the Python code that triggers the warning:

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")

Step-by-Step Breakdown:

Import necessary libraries: We start by importing plotly.graph_objects as go for creating the Plotly figure and streamlit as st for building the web application.
Create a Plotly figure: A simple go.Figure() is instantiated. This is our canvas for the visualization.
Add a trace: A go.Barpolar trace is added to the figure. This is just an example trace to ensure we have a valid Plotly figure to display; the type of trace isn't the cause of the warning.
Set initial layout dimensions: fig.update_layout(width=500, height=360) sets some base dimensions for the figure. Note that these might not be the dimensions that ultimately render if width="content" overrides them.
Display the chart with st.plotly_chart: This is the crucial line: st.plotly_chart(fig, width="content"). Here, we're telling Streamlit to render the Plotly figure, and importantly, we're specifying width="content". This argument instructs Streamlit to make the chart's width adjust dynamically to the width of its containing element in the app, making it responsive.

When you run this code in a Streamlit application (version 1.50.0 in the provided debug info), you will observe a deprecation warning in your console. This warning states: "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." The surprising part is that we haven't passed any arbitrary **kwargs. We've used fig (the Plotly figure) and width="content", which is a documented parameter for st.plotly_chart.

This example perfectly highlights the unexpected behavior. The warning appears to be triggered incorrectly for the width="content" parameter, indicating a potential bug or an overly aggressive warning condition within Streamlit's argument processing for this specific component. The intent of using width="content" is to achieve responsive chart sizing, a feature that should ideally work without triggering such warnings. The provided debug information (Streamlit 1.50.0, Python 3.14.2, macOS 26.1, Chrome) confirms the environment where this issue was observed, reinforcing that it's not an isolated incident but a reproducible problem within a specific version context.

The Expected vs. Current Behavior: What Should Happen and What Is

Let's clearly define what we anticipate when using st.plotly_chart and what is actually occurring. Understanding this gap is key to appreciating the issue.

Expected Behavior:

When you use st.plotly_chart(fig, width="content") or st.plotly_chart(fig, height="content"), the expectation is that Streamlit will render the Plotly chart, and its width (or height) will dynamically adjust to fill the available space in its container. This is a highly desirable feature for creating responsive web applications and dashboards, ensuring that visualizations look good on various screen sizes and within different layout configurations. Crucially, no deprecation warnings related to kwargs should appear. This is because width and height are documented parameters, intended for controlling the chart's dimensions, and they are being used as per the Streamlit API documentation.

If there were underlying changes to how width and height are handled, the expectation would be that the documentation is updated, and the transition is smooth. The width="content" parameter should work seamlessly without warning, or if it's truly deprecated in favor of a new method, the warning should accurately reflect that (e.g., warning about width itself being deprecated, not kwargs in general).

Current Behavior:

As reported, the current behavior is that st.plotly_chart(fig, width="content") does trigger a deprecation warning. The warning message is:

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 even though width="content" is a documented parameter and not a generic **kwargs being passed haphazardly. The internal logic within Streamlit, specifically the check for if kwargs: combined with how width="content" is processed, is causing this warning to be raised erroneously. It implies that internally, the width parameter might be caught in a broader kwargs processing block that is intended for truly arbitrary keyword arguments.

The core of the problem is that the warning is misleading. It suggests that you are misusing kwargs, when in fact, you are using a documented feature. This is why the report states, "Is this a regression? Yes, this used to work in a previous version." This indicates that a recent update to Streamlit has introduced this behavior, breaking the expected functionality for responsive chart sizing.

Essentially, the current behavior is: you try to make your chart responsive using a documented parameter, and Streamlit warns you that you're using deprecated arguments, which you aren't. This disconnect between the user's action, the documentation, and the warning message is the crux of the issue. The code works visually (the chart appears and is responsive), but the presence of the warning creates noise in the development process and can lead to confusion about best practices.

Debugging the Details: Unpacking the Streamlit Version and Environment

To effectively address this issue, it's crucial to understand the context in which it occurs. The provided debug information offers valuable clues:

Streamlit version: 1.50.0: This is a very important piece of information. Version 1.50.0 is specific, and knowing this allows developers to pinpoint when the behavior might have changed. If this was working in 1.49.0 but not in 1.50.0, it strongly suggests a regression was introduced in that particular release. This version specificity is key for tracking down the exact code change responsible for the warning.
Python version: 3.14.2: While the Python version is noted, it's less likely to be the direct cause of a Streamlit-specific component warning unless there was a very unusual interaction. However, it confirms the runtime environment.
Operating System: MacOs 26.1: Similar to the Python version, the OS is generally not the culprit for such specific component behavior warnings. It helps paint a complete picture of the user's setup.
Browser: Chrome: The browser is relevant for how the chart is rendered visually, but typically not for the Python-level warnings generated by Streamlit itself.

The Crucial `kwargs` Check:

The report also points to a specific code snippet introduced during recent changes (likely related to issue #XXXX and PR #YYYY which are placeholders in the original report):

if kwargs:
    show_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 block of code is the direct source of the warning. The problem is that when st.plotly_chart(fig, width="content") is called, the width parameter, intended for content-based sizing, is somehow being processed in a way that leads to this if kwargs: condition evaluating to True. This suggests that the width argument, or perhaps other arguments passed alongside it, might be falling into a generic kwargs bucket during the function's internal argument parsing, even though width itself is a specifically documented parameter.

The fact that this is a regression means that in a prior version of Streamlit, the width="content" argument was handled differently, perhaps by being processed before the general kwargs check, or by being explicitly excluded from it. The current implementation appears to be too broad and is incorrectly flagging a valid, documented use case as a deprecated kwargs usage. Understanding this specific code block and the context of Streamlit version 1.50.0 is essential for pinpointing the exact change that needs to be reverted or fixed.

Conclusion: Towards a Smoother Streamlit Experience

We've navigated the intricacies of the st.plotly_chart deprecation warning when using width="content". The issue, while seemingly minor, highlights the importance of precise argument handling in software development and the potential for unintended consequences during API evolution. The core problem is that a documented feature – responsive chart sizing via width="content" – is incorrectly triggering a warning about deprecated keyword arguments (kwargs). This is a regression that disrupts the clean developer experience Streamlit aims to provide.

The Streamlit team is aware of such issues and continuously works on refining the library. The intention behind these changes is to create a more robust and predictable API, guiding developers towards the best practices for building interactive applications. While the warning might be misleading in this specific context, it serves as a signal that the underlying mechanisms for handling arguments are being updated.

For users encountering this, the immediate solution often involves waiting for a patch release from Streamlit that addresses this specific regression. In the meantime, developers can choose to ignore the warning if the chart's functionality is correct, or explore alternative ways to manage chart dimensions if they arise. The long-term goal is to have width="content" work as expected without any spurious warnings.

This situation is a great example of the dynamic nature of software development. As frameworks like Streamlit grow and adapt, such minor bumps are often ironed out swiftly. We can look forward to future versions where this particular warning is resolved, allowing for seamless integration of responsive Plotly charts.

For more in-depth information on Plotly and its capabilities, you can always refer to the official Plotly Documentation. And for general Streamlit best practices and further discussion on component behavior, the Streamlit Community Forum is an invaluable resource.