Chat with GPT-5.4 for free

Live preview

See how GPT-5.4 thinks

Pick a task and watch a sample answer stream in. Open the same prompt in Chatday when you’re ready.

Why does this return undefined? const u = users.find(u => u.id = id)

The bug is in the arrow body: u.id = id assigns instead of compares, so the callback returns the assigned value and .find never matches the way you expect.

Fix it with a strict comparison:

const u = users.find(u => u.id === id);

Use === to compare. A single = is assignment, which is why you saw undefined.

Illustrative preview: your real answers run in Chatday. Continue in Chatday

Strengths

What makes GPT-5.4 stand out

Balanced speed and reasoning depth

1M-token context window

Reliable structured output

At a glance

GPT-5.4 specifications

1.1M

Context window

128K

Max output

Text · Vision · Code

Modality

Balanced

Speed

Free & Pro

Available in Chatday

Provider	OpenAI
Model family	GPT-5 series
Context window	1,050,000 tokens
Max output	128,000 tokens
Modality	Text · Vision · Code
Input price	$2.5 / 1M tokens
Output price	$15 / 1M tokens
Tool / function calling	Yes
Vision	Yes
Streaming	Yes
Available in Chatday	Free & Pro

Pricing shown for reference; usage is included in your Chatday plan.

Side by side

GPT-5.4 vs other top models

Compare

Model	Context	Best at	Input price	In Chatday
GPT-5.4	1.1M	Balanced	$2.5/M	Free
Claude Opus 4.8	1M	Frontier coding	$5/M	Free
Gemini 3.1 Pro	1M	Multimodal	$2/M	Free
Grok 4	1M	Realtime	$0.2/M	Free

FAQ

GPT-5.4 questions

Yes. GPT-5.4 is available on the free plan with daily limits. Pro raises the limits and adds priority access during peak times.

1.1M tokens: enough for very long documents, large codebases or extended conversations without losing earlier context.

Reach for GPT-5.4 on the tasks it’s built for, then switch models mid-chat in Chatday when another one fits better, no need to leave the conversation.

Yes. GPT-5.4 accepts image input, so you can share screenshots, diagrams and photos and ask it to reason over them.