the devil is in the details

Syllable breakdown

Dictionary meaning

a proverb expressing the idea that it is the small, specific details of a plan, contract, or design that contain the hidden difficulties — the traps, ambiguities, and complications that determine whether the overall project succeeds or fails; while the broad outlines of a proposal may appear straightforward and agreeable, the actual terms and specifications upon which success depends are often complex, contested, and full of potential problems that only become visible upon close examination; the phrase is particularly apt in the context of nanotechnology and precision engineering, where the performance of a device or material depends absolutely on atomic-scale precision — a few nanometres of misalignment or a single misplaced atom can be the difference between a functional quantum device and an inert structure; the idiom traces to the older expression God is in the details, attributed to architects and artists emphasising that the quality of a work is revealed in its smallest elements

Examples

• The contracts looked identical, but the devil was in the details — one clause shifted liability for delays entirely onto the supplier.
• In nanofabrication, the devil truly is in the details: a single monolayer of contamination can ruin months of work.