Which is cheaper, Grok 4.20 or GPT-5?

Grok 4.20 is the cheaper of the two: one 1,000-word request costs about 1,688 toman, about 3× cheaper than GPT-5.

Which one has the larger context window?

Grok 4.20, with 2,000,000 tokens.

Can I use Grok 4.20 and GPT-5 with one API key?

Yes. An uttapen key reaches every model unless you gave it an allowed-models list, and each request is charged in toman to the same wallet; only the model value changes.

Grok 4.20 vs GPT-5

Both sit behind the same key and the same code on uttapen — the only thing that changes is the model string, so you can run each of them against your own workload without touching anything else. On cost, Grok 4.20 comes out about 3× cheaper.

Feature	Grok 4.20	GPT-5
Provider	xAI	OpenAI
Model id	x-ai/grok-4.20	openai/gpt-5
Context	2,000,000 tokens	400,000 tokens
Max output	1,800,000 tokens	128,000 tokens
Input / 1M tokens	432,774 toman	432,774 toman
Output / 1M tokens	865,548 toman	3,462,194 toman
≈ one 1,000-word request	1,688 toman	5,063 toman
Input caching	69,244 toman / 1M	43,277 toman / 1M
Image input	Yes	Yes
File input	Yes	Yes
Tool calling	Yes	Yes
JSON output	Yes	Yes
Reasoning mode	Yes	Yes

Which one for what?

Grok 4.20

Multi-step problems, maths, and tracking down a bug
Whole documents or a codebase in a single request
Reading screenshots, invoices, and scanned forms
Agents that call your own APIs and database

1,688 toman per 1,000 words · Model page

GPT-5

Multi-step problems, maths, and tracking down a bug
Whole documents or a codebase in a single request
Reading screenshots, invoices, and scanned forms
Agents that call your own APIs and database

5,063 toman per 1,000 words · Model page

Run both with the same code

Swap the model value between the two ids and send the same request twice; what each answer cost comes back in the X-Uttapen-Cost-Toman header.

curlPythonNode.jsPHPGo

curl https://api.uttapen.ir/v1/chat/completions \
  -H "Authorization: Bearer sk-up-…" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "x-ai/grok-4.20",
    "messages": [{"role": "user", "content": "Introduce yourself."}],
    "stream": true
  }'

from openai import OpenAI

client = OpenAI(
    base_url="https://api.uttapen.ir/v1",
    api_key="sk-up-…",
)

stream = client.chat.completions.create(
    model="x-ai/grok-4.20",
    messages=[{"role": "user", "content": "Introduce yourself."}],
    stream=True,
)
for chunk in stream:
    print(chunk.choices[0].delta.content or "", end="", flush=True)

import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://api.uttapen.ir/v1",
  apiKey: "sk-up-…",
});

const stream = await client.chat.completions.create({
  model: "x-ai/grok-4.20",
  messages: [{ role: "user", content: "Introduce yourself." }],
  stream: true,
});
for await (const chunk of stream) {
  process.stdout.write(chunk.choices[0]?.delta?.content ?? "");
}

<?php
// composer require openai-php/client guzzlehttp/guzzle
$client = OpenAI::factory()
    ->withBaseUri('https://api.uttapen.ir/v1')
    ->withApiKey('sk-up-…')
    ->make();

$result = $client->chat()->create([
    'model' => 'x-ai/grok-4.20',
    'messages' => [['role' => 'user', 'content' => 'Introduce yourself.']],
]);
echo $result->choices[0]->message->content;

package main

import (
	"context"
	"fmt"

	"github.com/openai/openai-go"
	"github.com/openai/openai-go/option"
)

func main() {
	client := openai.NewClient(
		option.WithBaseURL("https://api.uttapen.ir/v1"),
		option.WithAPIKey("sk-up-…"),
	)
	resp, err := client.Chat.Completions.New(context.Background(), openai.ChatCompletionNewParams{
		Model:    "x-ai/grok-4.20",
		Messages: []openai.ChatCompletionMessageParamUnion{openai.UserMessage("Introduce yourself.")},
	})
	if err != nil {
		panic(err)
	}
	fmt.Println(resp.Choices[0].Message.Content)
}

model = "openai/gpt-5"

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Frequently asked

Which is cheaper, Grok 4.20 or GPT-5?: Grok 4.20 is the cheaper of the two: one 1,000-word request costs about 1,688 toman, about 3× cheaper than GPT-5.
Which one has the larger context window?: Grok 4.20, with 2,000,000 tokens.
Can I use Grok 4.20 and GPT-5 with one API key?: Yes. An uttapen key reaches every model unless you gave it an allowed-models list, and each request is charged in toman to the same wallet; only the model value changes.

More comparisons: all pairs · model rankings · full catalogue

base_url = https://api.uttapen.ir/v1