What is Ollama, and is it safe to run models locally?

What is Ollama?

Ollama is a model runner: it fetches a model file, loads it into memory and serves it to you through a command line, a desktop app and an HTTP API. Its GitHub repository is licensed MIT, and its README sums up the pitch as "Start building with open models." An open-weight model is one whose trained parameters you can download and run yourself, such as Google's Gemma or Alibaba's Qwen, as opposed to a model you can only reach through a company's servers.

You install it with one command, from the README read on 16 October 2026:

• macOS or Linux: curl -fsSL https://ollama.com/install.sh | sh
• Windows, in PowerShell: irm https://ollama.com/install.ps1 | iex
• Docker: the official image ollama/ollama on Docker Hub

Then ollama run gemma4 downloads Gemma 4 and opens a chat in your terminal. Programs talk to the same model through the REST API at http://localhost:11434/api/chat. Coding tools use that API: the README lists integrations for Claude Code, Codex, Copilot CLI and others, started with commands such as ollama launch claude. The local coding agent thread walks through those setups.

Does Ollama send your prompts anywhere?

Not when the model runs locally. The Ollama FAQ answers this directly: "Ollama runs locally. We don't see your prompts or data when you run locally."

The exception is cloud models. Ollama also offers models that run on its servers, and in its own examples their names end in cloud, such as gpt-oss:120b-cloud. For those, the FAQ says, "we process your prompts and responses to provide the service but do not store or log that content and never train on it." That is Ollama's policy statement, not something the editors can verify. If your code must not leave your machine, turn the cloud features off:

1. Open or create ~/.ollama/server.json.
2. Add { "disable_ollama_cloud": true }, or set the environment variable OLLAMA_NO_CLOUD=1 instead.
3. Restart Ollama.
4. Check the log for the line Ollama cloud disabled: true.

The FAQ notes that this also removes web search and cloud models. Pulling local models still needs the internet; Ollama fetches them over HTTPS.

Is the local API safe?

By default, yes for a single-user machine. The FAQ says: "Ollama binds 127.0.0.1 port 11434 by default." 127.0.0.1 is the loopback address, reachable only from the same computer. The catch is in Ollama's authentication page: "The local API at http://localhost:11434 does not require authentication." Any program running on your machine can use it, and if you widen the bind address, so can anything that reaches that address.

The FAQ shows how to widen it, with OLLAMA_HOST=0.0.0.0:11434, which listens on every network interface. Put those two facts together and the rule is simple: do not set 0.0.0.0 on a laptop that joins shared Wi-Fi or on a server with a public IP unless something else controls access. The FAQ's own suggestions for remote use are a reverse proxy such as Nginx or a Cloudflare Tunnel, which let you add sign-in in front of Ollama.

Browsers are a second door. The FAQ says Ollama "allows cross-origin requests from 127.0.0.1 and 0.0.0.0 by default", and you can allow more origins with OLLAMA_ORIGINS. Allowing chrome-extension://* lets every installed Chrome extension call your models, so name specific extensions instead.

What are the risks, side by side?

Risk	Default	What to do
Prompts leave your machine	Local models: no. Cloud models: yes	Disable cloud features if that matters
Other devices use your models	No; bound to 127.0.0.1	Leave OLLAMA_HOST alone, or put a proxy with sign-in in front
Web pages or extensions call the API	Only local origins allowed	Add specific origins, not wildcards
Old version with known bugs	Desktop apps download updates	Click "Restart to update"; update Linux installs yourself
Model licence terms	Varies by model	Read the model's licence before shipping its output in a product

On updates, Ollama's SECURITY.md recommends "Regularly updating to the latest version of Ollama", "Securing access to hosted instances of Ollama" and "Monitoring systems for unusual activity", and asks that vulnerabilities be reported privately through GitHub advisories. The FAQ says the macOS and Windows apps download updates automatically; you apply them with "Restart to update".

Is the model itself safe?

Running a model locally keeps your data private; it does not make the model's output correct. A local model writing code will still invent functions and packages; one study, Spracklen et al., found average package hallucination rates of at least 21.7% for open-source models and 5.2% for commercial ones. The local models prompt thread lists the checks the editors apply to anything a local model writes, and the LLM explainer covers why. Licences differ by model too: the CodeLifter local models page lists eight models with licences ranging from Apache 2.0 and MIT to the Gemma Terms of Use, checked on 15 October 2026.

Short version

• Ollama is an MIT-licensed runner for open-weight models, with a local API on port 11434.
• Local models keep prompts on your machine; model names ending in cloud do not.
• The API binds to 127.0.0.1 and has no authentication, so never expose it without a proxy that adds sign-in.
• Disable cloud features with OLLAMA_NO_CLOUD=1 if your code must stay local.
• Keep it updated, and check each model's licence.