OpenAI Codex examples: 11 real use cases with prompts
Source-checked cases, each with what happened and the prompt.
Includes cases labeled Codex (5), OpenAI Codex CLI (4), OpenAI Codex (1), OpenAI Codex (ChatGPT desktop, voice mode) (1). Each case keeps the label its source used.
- Import every saved Instagram food reel into a self-hosted recipe app with a pipeline Codex wroteRecreated promptEvidence: Screenshots or logs
Karan Sharma gave Codex access to all their saved Instagram food reels and asked it to import them into their self-hosted Mealie recipe instance. Codex wrote a pipeline on the fly and ran each reel through it: yt-dlp pulls the audio, Whisper transcribes it, Gemini 3.8 Flash formats it as a recipe and it's sent to Mealie. Sharma calls it very useful.
Codex · Coding · Source date:
- Work out why a meeting was missed and set up a tested email-to-calendar check with ChatGPT and CodexRecreated promptEvidence: Described by poster
Dave W Plummer missed an important appearance and asked the ChatGPT desktop app, which has access to their Gmail, to work out how it happened. It found Plummer had noon in mind, the time of an earlier prep call, while the event started at 7:50 a.m. Pacific, with emails also mentioning 8:50 a.m. Mountain. When Codex then reconstructed the email trail, it found the organiser had cancelled the calendar invite sent to Plummer's regular address while sorting out a Teams login mismatch, and the later confirmation email had no new invite. With Codex, Plummer then set up a recurring agent that reads email threads, including changes and cancellations, adds missing calendar entries with the source email and link, and flags contradictions. Test alerts at first didn't notify on the iPhone; after checking alarms, sync and Focus settings, a test finally rang. It now checks every ten minutes while the Mac is awake; its first historical review was still running.
ChatGPT, Codex · Personal · Source date:
- Find two seven-seat rental cars far cheaper through a reseller discount with Codex searching every membership and siteRecreated promptEvidence: Described by poster
Xcelerate needed two rental cars that could each carry seven people for a trip to Maine, and had memberships with Avis, Hertz, Costco and Chase's travel portal; checking every combination by hand would have taken forever. They wrote a Codex prompt in 20 minutes and let it use the browser directly. It queued any CAPTCHAs for them to solve, and a sub-agent searched Reddit for other people's ways of getting good rental deals. It found a third-party Avis reseller charging $600 with a discount code, against $1,100 cheapest from Avis directly. By those quoted prices that's about $500 less for both cars (the poster calls it a $1,000 saving), and they say they wouldn't have found it without about a week of manual searching.
Codex · Travel · Source date:
- Build a family meal-prep system from fridge photos with weekly plans, one grocery list and cost per meal using ChatGPT and CodexRecreated promptEvidence: Described by poster
Cooking for a household with mixed needs (no red meat for one, extra protein for another, a baby, and occasional guests), Fei Jiang used GPT and Codex to build a 'Meal Prep OS'. It reads a fridge photo to see what's there and what should be used soon, builds a weekly plan with reused ingredients and a prep sequence, makes one consolidated grocery list to paste into a delivery app, and estimates nutrition and cost per meal and serving.
ChatGPT, Codex · Personal · Source date:
- Find, negotiate and review a small office lease with CodexRecreated promptEvidence: Described by poster
Codex found a 74 sq ft commercial lease near the poster's kids' school, negotiated the terms and reviewed the contract; the poster found it cheaper than a coworking desk.
Codex · Ops · Source date:
Talking to Codex in voice mode while cooking dinner, the author got a Django newsletters archive with four importers and a pull request, then finished the rest with typed prompts.
OpenAI Codex (ChatGPT desktop, voice mode) · Coding · Source date:
- Automate defect remediation across C/C++ codebases with Codex CLIRecreated promptEvidence: Company case study
According to OpenAI's case study, Cisco's Codex CLI defect-repair workflow raised defect resolution throughput 10–15x, and Codex build optimization saved more than 1,500 engineering hours a month.
According to OpenAI:10–15x defect resolution throughput
OpenAI Codex CLI · Coding · Source date:
- Turn podcast highlights into timestamped clips with Claude Cowork + Claude in Chrome + CodexRecreated promptEvidence: Described by poster
Claude Cowork expanded the poster's top 10 podcast takeaways, then used Claude in Chrome to find the transcript and timestamps for each clip, and Codex downloaded them.
Claude Cowork, Claude in Chrome, OpenAI Codex · Content · Source date:
- Port an HTML5 parser from Python to JavaScript with Codex CLIEvidence: Screenshots or logs
Codex CLI (GPT-5.2) ran for hours largely unattended and produced about 9,000 lines of dependency-free JavaScript passing 9,200 html5lib tests, in about 4.5 hours start to finish.
Poster says:Passes 9,200 html5lib tests
OpenAI Codex CLI · Coding · Source date:
- Compare Claude Code, Codex and Gemini CLI on a 97k-message chat datasetRecreated promptEvidence: Described by poster
The poster gave the same 97k-message WeChat dataset to Claude Code, Codex and Gemini CLI as analysts and published results with an evaluation table.
Claude Code, OpenAI Codex CLI, Gemini CLI · Data · Source date: