The name promises more than the API delivers, and that is the first thing worth clearing up.
GPT-4o was introduced as OpenAI's omni-era model, and the demos showed voice and vision working together in real time. Through the API you get text and image input, and text output. No generated speech, no generated images. If you budgeted for a single model to handle a voice product end to end, budget again.
What you do get is a dependable general-purpose model with one genuinely clever pricing feature.
Caching is the reason to read the invoice
GPT-4o runs about $2.50 per million input tokens and $10.00 per million output tokens. Cached input drops to roughly $1.25 per million — half price.
That discount is not a rounding detail; it changes which architectures make sense. Any design that resends a stable prefix on every call — a long system prompt, a product catalogue, a policy document, a fixed few-shot block — pays half for that portion once it is cached. Structure prompts so the stable material sits at the front and the variable part at the end, and the saving arrives without changing a line of application logic.
Get the order backwards and you pay full price for the same tokens. It is the cheapest optimisation available here and the one most often missed.
Where its age shows
The knowledge cutoff is October 2023.
Measured against today that is a long silence. Anything released, renamed, repriced or deprecated since then is invisible to the model unless you put it in the prompt yourself. For a support assistant answering questions about your own product that hardly matters, because your documentation is in context anyway. For anything that reasons about the current state of the world, it matters a great deal, and retrieval stops being optional.
Context is 128,000 tokens. Respectable when it launched, ordinary now that million-token windows are widely available.
What it is still good at
Output ceiling is 16,384 tokens — double what several contemporaries allowed, and enough for a substantial file or a long structured response in one pass.
It calls tools reliably, it handles images without a separate vision pipeline, and it is probably the most thoroughly documented model in production anywhere. When something behaves oddly at two in the morning, someone has already written up the fix. That is worth more than a benchmark point.
Specifications
| Field |
Value |
| Provider |
OpenAI |
| Context window |
128,000 tokens |
| Maximum output |
16,384 tokens |
| Knowledge cutoff |
October 2023 |
| Input |
text, image |
| Output |
text |
| Tool calling |
Supported |
| Reasoning mode |
Not supported |
| Indicative pricing |
$2.50 in / $1.25 cached in / $10.00 out per million |
| Released |
13 May 2024 |
Pricing and availability change; confirm against your own account before you plan a budget around them.
See how it stands against newer options in the AI model directory, or read Gemini 2.5 Flash if the 128K window is what you are trying to escape.