Back to Blog
3 min read

UI vs. API: Unveiling the Key Differences in Today's Top AI Chat Engines

What we see in the user interface—rich citations, web search, advanced reasoning—doesn't always match what an API actually delivers. Here's a concise but technical look at the differences.

xFunnel Team
xFunnel Team
UI vs. API: Unveiling the Key Differences in Today's Top AI Chat Engines
xFunnelxFunnel Team

Models Comparison

CompanyModelSourceCitationsDepth
OpenAIChatGPT (Unauth)Pre‑trainedOnly in "Search" modeSummaries
ChatGPT (Free GPT‑4o)Pre‑trainedOnly in "Search" modeDetailed, nuanced
ChatGPT o1Pre‑trainedNone by defaultThorough, accurate
ChatGPT o1 ProPre‑trained, no webNone (reasoning)Very deep reasoning
OpenAI API (GPT‑4o)Model onlyNo autoCapable; can be lengthy
OpenAI API (GPT‑latest)Model onlyNoneFast, concise
GoogleGoogle Gemini 2.0 Flash UISGE (RAG) or training dataNot Always (SGE)Rich, large context
Google Gemini 2.0 Flash APIDev chooses (tools)Possible customSame as UI
PerplexityPerplexity AI (UI)Always search (RAG)Yes (each statement)Concise, factual
Perplexity AI (API – Sonar)Real-time search (RAG)YesMulti-step reasoning
AnthropicClaude 3.5 Sonnet (UI)Pre‑trained onlyNoneVery detailed, large context
Claude 3.5 Sonnet (API)Pre‑trained onlyNoneSame model, structured outputs
MicrosoftMicrosoft Copilot (Bing)Bing search (RAG)Yes (footnotes)Moderate detail
DeepSeekDeepSeek L1 (UI)Pre‑trained onlyNone autoSummaries, references
DeepSeek R1 (UI)Hybrid search (RAG)Some links/URLsVery in-depth, iterative
DeepSeek L1 (API)No webNoneSimilar to UI
DeepSeek R1 (API)Web search (RAG)Partial referencesDetailed chain-of-thought

UI vs. API Realities

Although user-facing chat UIs seem to provide rich references, live web access, or advanced reasoning, the API behind them often delivers a more bare-bones experience. A chatbot may show footnotes, clickable sources, or large context windows in its interface—yet when developers call the same model programmatically, they may only get raw text without citations or any guarantee of real-time search.

Key Differences

  1. Citations and Live Data

    • UI: Many chat UIs overlay search results or footnotes, giving the illusion of real-time knowledge.
    • API: Typically provides only the model's raw text output. Developers must add their own retrieval or citation logic.
  2. Model Versions and Modes

    • UI: Often gives simplified toggle options ("with browsing," "without browsing," "deep reasoning," etc.).
    • API: You select a model endpoint, but it won't magically fetch web data or reformat for references unless you implement it.
  3. Depth of Reasoning

    • UI: May appear to reason in steps (chain-of-thought) or offer extended memory.
    • API: Usually requires you to structure prompts and maintain conversation state. You see only final answers, not intermediate reasoning.
  4. Speed and Limits

    • UI: Platforms optimize performance and handle usage limits behind the scenes.
    • API: You must handle rate limits, tokens, or usage fees on your own, and performance can vary based on your implementation.

In short, the user interface can mask complexities. If you rely on an API, you won't automatically get those same features; it's up to you to replicate or enhance them. This is important when building custom applications: your end users won't see the fancy UI features unless you explicitly implement them or incorporate external data sources yourself.

Conclusion

For developers and businesses aiming to leverage AI capabilities, understanding these UI vs. API discrepancies is crucial. The polished experience you see when chatting with a model on a web interface may not reflect the raw data or response style you'll receive directly from an API. By carefully configuring prompts, hooking into search APIs, or building your own citation mechanisms, you can recreate (and sometimes surpass) the functionality of the official UI—just don't assume you'll get it "out of the box."