What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
JSON.parse() throws a SyntaxError when the text it receives is not valid JSON. Check the reported location and nearby punctuation, then confirm the input is actually JSON—not an HTML error page, empty response, or already-parsed value. The fixes below cover both malformed JSON strings and unexpected API responses.
Start by checking the exact input
Before changing code, preserve and inspect the precise string passed to JSON.parse(). A parser’s reported line, column, or position is a clue, not always the location where the mistake began: a missing quote or comma earlier in the text can make a later character appear to be the problem. Error wording and position formats vary between browsers and JavaScript runtimes. MDN’s JSON.parse error reference documents several of these variations.
try {
const value = JSON.parse(rawText);
// Use value after parsing succeeds.
} catch (error) {
console.error("Could not parse JSON", error);
console.error("Raw input:", rawText);
}For a long payload, inspect the text around the indicated location and the preceding delimiter. If it came from a request, log or view the raw response body before trying to repair it.
Fix common JSON syntax errors
JSON looks similar to a JavaScript object literal, but it follows its own stricter grammar. RFC 8259 defines JSON’s syntax and valid values; the examples below show common ways JavaScript-like text can fail when passed to JSON.parse().
Free tools Windows power users keep installed
One-click scans. No signup required.
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
Use double quotes for strings and property names
JSON strings and object property names must use double quotes. Single-quoted JavaScript strings are not valid JSON.
// Invalid JSON
{'name': 'Ada'}
// Valid JSON
{"name": "Ada"}Remove trailing commas
Do not leave a comma after the last item in an array or object.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
// Invalid JSON
[1, 2,]
{"name": "Ada",}
// Valid JSON
[1, 2]
{"name": "Ada"}Correct number syntax
JSON numbers cannot have leading zeros except for zero itself. A decimal point and an exponent must be followed by digits; for example, 1. is invalid, while 1.0 is valid. Use a complete exponent such as 1e3, not 1e or 1e+. NaN and Infinity are not JSON numbers.
// Invalid JSON fragments
01
1.
1e+
NaN
Infinity
// Valid JSON fragments
0
1.0
1e3Use lowercase JSON literals
The JSON literals are exactly true, false, and null, all lowercase. JavaScript values such as undefined are not JSON values.
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Close every string and structure, and remove extra text
Finish every quoted string, array, and object; complete escape sequences and exponents; and ensure there is no non-whitespace text after the single JSON value. JSON text may be an object or array, but it can also be a number, string, boolean, or null. A raw line break inside a quoted string is invalid; quotation marks, reverse solidus characters, and control characters must be escaped according to JSON string rules.
// Invalid: missing closing bracket
[1, 2
// Invalid: extra text after the value
{"ok": true} done
// Valid
[1, 2]
{"ok": true}Check whether an HTTP response is JSON
A parsing error does not prove that the server sent malformed JSON. It may have returned an empty body, plain text, an HTML error document, or other non-JSON content. Check the request’s status and actual response body in the browser’s Network panel before changing the data or parser. These are possibilities to investigate for a particular endpoint, not assumptions about every failed request.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
Use Response.json() only for a JSON response body
Response.json() reads the response body and parses it as JSON; it rejects with a SyntaxError if the body cannot be parsed. See MDN’s Response.json() documentation.
const response = await fetch("/api/data");
console.log("HTTP status:", response.status);
const rawText = await response.text();
console.log("Raw response body:", rawText);
try {
const data = JSON.parse(rawText);
console.log(data);
} catch (error) {
console.error("Response body was not valid JSON:", error);
}This diagnostic reads the body as text and parses that text once. In normal code, if the endpoint returns JSON and you do not need to inspect the raw body first, use const data = await response.json() instead. Do not consume the same response body as text and then attempt to read it again with response.json().
The Tool Desk
Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Rule out a mistaken second parse
response.json() already parses a JSON response body and returns a JavaScript value. Passing that value to JSON.parse() again is not the same as parsing the original response text: JavaScript first coerces the value to a string, which may not be JSON. Check the value’s type and the exact expression that failed before adding or removing a parse call.
Prevent malformed JSON at its source
When the source is a JavaScript value, use JSON.stringify() to serialize it instead of assembling braces, quotes, and commas manually. When the source is external text, fix the producer where possible and retain the raw payload while debugging. Do not use eval() as a workaround: it executes JavaScript and does not validate that input conforms to JSON grammar.
const payload = { name: "Ada", active: true };
const rawText = JSON.stringify(payload);
const copy = JSON.parse(rawText);MDN’s JSON.parse() reference describes parsing behavior and related JSON APIs. RFC 8259, the JSON data interchange standard, states that a JSON parser must accept texts that conform to the JSON grammar.
Or skip the browser setup
If you are diagnosing a page whose rendered content is behind an error or consent screen, a screenshot can help you inspect what the browser receives. ScreenshotNeo is a website screenshot API and MCP server; it is not a JSON parser and does not replace inspecting an API response body. Its one-call capture can show the rendered page:
Quick Recap
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpSee the ScreenshotNeo API documentation for request options. Cookie banners, popups, and chat widgets are removed before the shot; bot checks, blank pages, and failed loads are never billed; an MCP server lets AI agents take screenshots. The free plan includes 1,000 screenshots a month with no card, and paid plans start at $5 for 3,000. Sign up for the free plan.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
