Why ChatGPT 5 is Glacially Slow on Long Chats and What to Do About It

ChatGPT 5 is the newest and most powerful version of OpenAI’s tool. OpenAI says it is their fastest and smartest model yet, and it can give expert answers in many areas. The company says it can help with school, work, coding, writing, and personal tasks. In its release, OpenAI promised that GPT-5 is “our smartest, fastest, most useful model yet.” You can read this in the official OpenAI announcement for GPT-5.

Don’t miss our follow-up article: 10 Quick Ways to Make GPT-5 Faster in Chrome, Safari, and Firefox — Faster in 2 Minutes

Many news sites reported on the launch with excitement. They said GPT-5 is better at understanding questions and giving clear answers. It is faster than earlier versions, and it makes fewer mistakes. Some reviews even said it feels like talking to a human expert. That mix of speed and power is why many people started using it right away.

But there is also another side. The promise sounds wonderful, yet the day-to-day use can be frustrating. The tool does answer with detail and depth, but the longer you chat, the slower the system feels. What should be smooth can turn into a painful wait. The gap between promise and use is essential, and this article will explain why it occurs and what you can do about it.

The Slowness Problem

When you start a new chat in GPT-5, the system feels quick. Answers come smoothly, and the text appears almost in real time. However, as the chat becomes longer, the entire page slows down. A recent thread on Reddit shows that users see the same painful lag.

The slowdown is easy to measure. A simple reply from the server might finish in 13 seconds, but the user sees the reply take 240 seconds to load on the screen. That is a four-minute delay. The problem is worse with code. In my experience, a code reply that the server builds in 20 seconds can take 15 minutes to render in the browser.

This level of delay is significant because many people use GPT-5 for professional purposes. If you need an answer fast, a four-minute lag feels endless. If you are debugging code, a 15-minute wait is a deal breaker. In the following sections, we will examine the technical reasons behind this slowdown and then discuss practical steps you can take when you encounter it.

Restarting Chats

One common way to fix the slowdown is to end the current chat and start a new one. Many users write a summary at the end of a long thread. Then they copy it into a new chat to keep the work going. This clears the page and makes the system feel fast again.

But this method has a very big cost. When you restart, you lose the memory of the long session. The model forgets names, steps, and choices you built up before. A user on Reddit Pro explained that even simple back-and-forth threads become sluggish, and restarting breaks the flow.

Currently, the ChatGPT interface does not allow you to archive or collapse the top of a lengthy chat. The full thread always stays in the browser’s memory. The load is applied only to the front end. It has nothing to do with GPT server performance or context size. It has everything to do with a poor UI design that cannot handle long threads.

Technical Causes of the Slowness

The primary reason for the slowdown is how the ChatGPT interface handles lengthy conversations. Every single message stays active in the page. The browser must keep the entire thread in memory, even if you only see the last few lines. Each new answer forces the browser to recalculate the layout for the whole of the thread. That takes time and makes the page freeze.

Another cause is the excessive use of regular expressions. The system utilizes regular expression (regex) rules to identify links, style text, and format code blocks. Regex is fine for short text, but it is slow for long pages. As the chat grows, each new answer makes the regex scan more text. That puts extra load on the browser and slows down typing, scrolling, and rendering.

Code replies add even more weight. Each block of code is styled and colored. A large block of code can take far longer to render than plain text. This is why a code reply can take 20 seconds on the server but 15 minutes to show up in the browser. As one post on the Cursor forum shows, many users now call it “painful to use.”

Always use GPT-5 Fast Mode

You can also set GPT-5 to Fast mode before you begin. The dropdown at the top of the chat lets you pick Fast, Thinking, or Auto.

Fast mode makes ChatGPT answer quickly with short reasoning. Thinking mode makes it write longer answers with deep steps. Auto switches between them. For best performance, choose Fast. This setting keeps replies short and helps prevent the slowdown that comes with long chats.

Rules Before Chat

One way to reduce slowness is to set rules before the chat begins. ChatGPT follows instructions better when they are firm and clear. Soft requests, such as “please be brief,” often fail. Strong commands with words like Always and Never work better. For example, you can write: “Always answer in short sentences. Never give more than three sentences unless I ask.”

Paste these rules at the start of every chat:

• Always answer in short sentences.
• Do not use regex to update text.
• Never give more than three sentences unless I ask.
• Always keep answers under 100 words.
• Never add explanations before the answer.
• Always wait for me to ask if I want details.

You can set these rules in the ChatGPT UI before you start. Go to Custom Instructions in the settings. Write your rules clearly. Use strong words like Always and Never. Remember, you are talking to a machine that has no feelings, and not a person who might feel offended by plain language.

When you start a new chat, the model will follow these rules from the first message. Also note that the GPT-5 UI has a mode switch at the top. It can be set to Fast, Thinking, or Auto. For most work, change it to Fast. This setting reduces heavy processing and keeps the chat responsive.

If you have a project, enter rules using the Custom Instructions box in ChatGPT:

1. Open settings.
2. Go to Custom Instructions.
3. Type your rules in the boxes.
4. These rules apply to every new chat until you change them.

If you do not have a project, set rules at the start of any chat:

1. Begin the chat with a rule message.
2. For example: “Always answer in short sentences. Never give more than three sentences unless I ask.”
3. ChatGPT will follow these rules for that session only.

Rules During Chat

Even with good rules set at the start, long chats can still slow down. When you notice answers getting heavy or delayed, you can add or update rules inside the same chat. ChatGPT will update the rules mid-chat if you give an explicit instruction, so you do not need to restart.

For example, you can say: “From now on, never use long lists.” Or you can say: “Always give one sentence answers until I say otherwise.” You can also say: “Stop giving steps, just give the command.” That direct instruction makes the model reset its style and handle the chat in a simpler way.

This method works because the slowness is linked to the amount of text displayed. By adjusting rules while the chat is active, you keep the session lighter and stop the problem before it grows. It is a simple way to manage the session without losing context.

In FireFox, if it is code generating and Firefox prompts “this page is running slow” you can stop the page, and refresh, and your code is all generated. The backend generation is complete; the part that is running slow is the UI update which can take as long as 45 minutes for one piece of code.

A Message to OpenAI

The slowdown in long chats is not caused by the model. It is caused by the way the client-side browser interface handles long threads. It does not change if you use Chrome, Firefox, or any other browser. The idea of keeping every message active in the browser, even when the user only needs the last few lines, is counterproductive. The interface also runs heavy regex checks and code formatting on every block of text.

The solution is to collapse the model periodically, reduce the ability of the user to scroll up (they are not likely to) and to focus on the Human Interaction rather than the past history of this chat. That’s the whole idea of context: ChatGPT has the context, but the human has their memory.

The front-end design is a weak point that undercuts the power of GPT. Power users face long waits, frozen screens, and lost time because the UI does not scale to chats longer than 15 minutes. And your QA department is either not testing this, or your management is not listening to QA, because power users are important. Performance is important.

A few small changes, such as collapsing old messages or allowing GPT to archive earlier parts of the visible client-side thread, will fix much of the slow chat problem. Don’t make excuses – just do it, it will only take a couple days work. That’s a fraction of the time a million users are wasting today.

Preserving Context in a New Chat

When a chat becomes too slow, sometimes you have no choice but to start a new one. This clears the page and makes the system fast again. But the problem is that ChatGPT forgets everything from the old thread. It forgets the names of modules, the design choices, and even the step order you built over hours. In coding work, this can undo four or five hours of progress.

The best way to minimize damage is to create a backup before restarting. You can ask ChatGPT to build this record for you. Some valid requests are:

• “Make a summary of the project so far with all key steps.”
• “List all external file names we have used so far.”
• “List all modules we have created in this session.”
• “List all environment variables we defined and their values.”
• “List all table names and column details we have created.”

Copy the summary into a text file on your computer. When you start a new chat, paste the summary at the top. If your work uses files, you can also have ChatGPT make a list of them. Then place those files in the new chat using the file upload area. This gives the model both the written context and the linked files it needs to continue.

It will not be perfect. The new chat will not remember details the way the old one did. However, the summary and file list will save you from having to start from scratch. Until OpenAI adds a better way to carry context across threads, this is the only reliable method.

Summary

ChatGPT 5 is a powerful tool that promises speed and expert answers. However, the user interface struggles to handle lengthy chats effectively. The slowdown comes from the browser, not from the AI or the server. The design keeps every message active, runs regex on huge blocks of text, and takes far too long to render code.

Your performance will be better if you set the rules before you start and update them during the session. You can also protect your work by asking ChatGPT to create summaries, list files, modules, and tables, and then saving that record before you restart.

You can use these tips to prevent the worst of the slowdown and keep your projects moving forward. ChatGPT 5 has great power, but a better UI design is needed to unlock its full promise.

Don’t miss our follow-up article: 10 Quick Ways to Make GPT-5 Faster in Chrome, Safari, and Firefox — Faster in 2 Minutes

Have you seen this slowdown? Share your own fixes in the comments below