Overview
GPT-5 was OpenAI's flagship reset in August 2025, replacing the sprawl of GPT-4o, o3 and friends with a single unified system that automatically routes a query to a fast model or a deeper reasoning model. It delivered large gains in coding, math and factual reliability over GPT-4o, and dramatically reduced hallucinations on open-ended questions, positioning OpenAI back at the frontier after a year of fierce competition.
The launch was not flawless — some users missed GPT-4o's personality and the router occasionally under-thought simple prompts — but GPT-5 set the architecture that 5.1 and 5.2 refined. It remains a capable, widely available model and the baseline that the rest of the 5-series builds on.
What it can do
- Unified router picks fast vs deep reasoning automatically
- Major coding and math gains over GPT-4o
- Sharply reduced hallucination rate
- Broad availability across ChatGPT and API
Pricing: Mid-to-high tier; cheaper than 5.1/5.2.
Benchmarks
- Coding
- Big jump over GPT-4o
- Hallucinations
- Substantially reduced
Pros and cons
What works
- Strong all-round reasoning and coding
- Lower hallucination rate than predecessors
- Auto-routing simplifies model choice
Trade-offs
- Router can under-think easy prompts
- Tone felt flatter than GPT-4o at launch
- Outclassed by 5.1/5.2 on nuance
The verdict
GPT-5 was the architectural turning point for OpenAI — reliable, far less prone to hallucination, and the platform the 5-series now stands on. It's still a solid choice on a budget, but most users will prefer the refinements in GPT-5.1 or GPT-5.2.
Best for: A dependable, lower-cost entry point to the GPT-5 family.
Questions
What changed with GPT-5 versus GPT-4o?
GPT-5 unified OpenAI's models behind an automatic router, improved coding and math, and cut hallucinations significantly compared with GPT-4o.
Is GPT-5 still worth using?
Yes, especially on a budget, but GPT-5.1 and GPT-5.2 improve tone, instruction-following and top-end reasoning.