---
id: "2024-07-23-llama-3-1-405b"
url: "https://postcutoff.com/e/2024-07-23-llama-3-1-405b/"
as_of: "2026-11-13T13:49:00+01:00"
date: "2024-07-23"
date_precision: day
category: open-source
importance: 4
confidence: high
status: [Confirmed]
sources: 2
editor: human editor
human_review: null
version: "2026-10-04"
---

As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/e/2024-07-23-llama-3-1-405b/

# Llama 3.1 405B: the first frontier-class open-weights model

Meta released Llama 3.1 including a 405B-parameter model with 128K context, which Meta said was competitive with GPT-4o and Claude 3.5 Sonnet — the first openly downloadable model at the frontier.

## Key facts
- Released 23 July 2024
- Sizes: 8B, 70B, 405B; 128K context
- 405B trained on over 15T tokens using more than 16,000 H100 GPUs
- Mark Zuckerberg published 'Open Source AI Is the Path Forward' alongside

## What happened

Meta released open weights for a dense 405B model along with a detailed technical report.

## Why it matters

Narrowed the open–closed gap to months; open frontier weights reshaped policy debates and enabled wide distillation.

## Your AI and this story

- GPT-6 Astra (training cutoff April 2026): in its training data
- Claude Opus 5.5 (training cutoff June 2026): in its training data
- Gemini 4 Hydrogen (training cutoff March 2026): in its training data
- Grok 4.7 (training cutoff May 2026): in its training data

## Sources

1. [Introducing Llama 3.1 (Meta AI)](https://ai.meta.com/blog/meta-llama-3-1/) (ai.meta.com, official)
2. [The Llama 3 Herd of Models (arXiv)](https://arxiv.org/abs/2407.21783) (arxiv.org, paper)

## Changes

- 2026-09-29 (filed): Created

## Related

- 2025-04-05: [Meta releases Llama 4 Scout and Maverick](https://postcutoff.com/e/2025-04-05-llama-4/index.md)
- 2024-04-18: [Meta releases Llama 3 (8B, 70B)](https://postcutoff.com/e/2024-04-18-llama-3/index.md)
- People: [Mark Zuckerberg](https://postcutoff.com/person/mark-zuckerberg/)