Open WebUI vs LocalAI

These are not substitutes. Open WebUI is a user interface that talks to a model server; LocalAI is the model server. Installing one does not get you the other, and the comparison only makes sense once you know which half you already have.

That is also why their RAM figures look so different. Open WebUI's 2 GB floor is the web app plus its database. LocalAI's 8 GB floor is the memory for the models it has loaded at once — the app itself is not the cost.

Pick Open WebUI if

• You already run Ollama on :11434 and want a browser front end with accounts, saved history and a sidebar.
• More than one person will use it. Per-user accounts and per-user history are the reason to install it rather than point everyone at the raw API.
• You want document upload and RAG without building a pipeline: drop a PDF in, it chunks, embeds and cites back.
• A single container behind your existing reverse proxy is the whole deployment.

The memory caveat is honest and worth repeating: Open WebUI idles at a few hundred megabytes, but a resident 7B model behind it on a 4 GB board is a fully committed machine. Front end + Ollama + one model is roughly the whole 4 GB. 8 GB is where that combination stops being tight.

Pick LocalAI if

• A script or an app needs a drop-in OpenAI replacement — set base_url, keep the client.
• You need more than chat from one endpoint: embeddings, speech-to-text and image generation behind the same API.
• You want several models loaded simultaneously and routed by model name.
• You are comfortable with a directory of YAML model files and know which backend you want.

The sizing rule that matters here is not "how big is my model" but "how big is the sum of the models loaded at once". Chat plus embeddings plus whisper on one low-spec board is a swap storm, and no amount of tuning fixes a working set larger than the RAM.

The number that decides it

Both pages carry the same caveat: their figures come from documentation, not from our own benches. What we have measured on this hardware is the storage side — the same interface went from 24 seconds to 0.25 seconds for its first paint when the database moved from a 5400 rpm 2.5" drive to a cheap SATA SSD. Whichever of these two you install, put its database on the SSD and its bulk files on the spinning disk.

Memory bandwidth is the other ceiling nobody mentions. Our box moves 5.06–5.25 GB/s, and a 7B model at Q4 is about 4.4 GB read per token, so roughly one to two tokens a second is the arithmetic ceiling no matter which front end is drawing the text.

Verdict

Install Open WebUI when you have a model server and no interface — that is the common case, and it is the smaller commitment of the two.

Install LocalAI when the thing missing is the API: a client that expects OpenAI-shaped endpoints, or a script that needs chat and embeddings without three separate daemons. If all you want is one chat model behind a nice UI, LocalAI adds configuration surface you will not use.

They are not mutually exclusive. LocalAI can sit behind Open WebUI the way Ollama does, because both speak the same OpenAI-compatible shape. Pick the layer you are missing, not the one with the better screenshot.