故障 vs 不具合 vs エラー vs バグ: Japanese Tech Trouble Words for Broken Devices, Malfunctions, Errors, Bugs, Apps, and Customer Support

Your phone just went black and won’t turn on. Your app crashes every time you open it. A red error message appears on screen. Or your developer friend tells you there’s a bug in the code. In English, you might describe all of these situations as “something is broken” — but in Japanese, each problem has its own specific word.

Japanese makes important distinctions depending on what broke, how it broke, and who is describing the problem. If you ever need to call Japanese customer support, file a bug report, or simply read an error message on your screen, knowing the right word makes all the difference between sounding fluent and sounding lost.

In this article, we compare four key Japanese tech trouble words: 故障（こしょう）, 不具合（ふぐあい）, エラー, and バグ — plus a handful of related terms that show up constantly in tech contexts.

Quick Answer: 故障 vs 不具合 vs エラー vs バグ

In English, “problem” covers all four of these. In Japanese, the word you choose signals exactly what kind of trouble you mean — and using the wrong one can make your report confusing or sound unnatural to a native speaker.

故障 in one sentence

スマホが故障した。
Sumaho ga koshou shita.
My smartphone broke down (is physically damaged / not functioning).

不具合 in one sentence

アプリに不具合が発生しています。
Apuri ni fuguai ga hassei shite imasu.
A malfunction has occurred in the app.

エラー in one sentence

ログインしようとすると、エラーが出ます。
Roguin shiyou to suru to, eraa ga demasu.
When I try to log in, an error appears.

バグ in one sentence

このアップデートでバグが修正されました。
Kono appudēto de bagu ga shuusei saremashita.
The bug was fixed in this update.

What Does 故障 Mean?

故障（こしょう）refers to a physical breakdown — a real-world device or machine that has stopped working. The word is rooted in the idea of something being damaged or disabled, which is why it applies almost exclusively to hardware: smartphones, computers, appliances, vehicles, vending machines, and elevators.

You will often see 故障中（こしょうちゅう）on signs, meaning “out of order.” If something is beyond simple adjustment and needs to go to a repair shop, 故障 is the right word.

Related words: 修理（しゅうり）= repair / 修理に出す = to send for repair / 故障中 = out of order

Example 1
スマホが突然故障して、データがすべて消えてしまいました。
Sumaho ga totsuzen koshou shite, dēta ga subete kiete shimaimashita.
My smartphone suddenly broke down and all my data was lost.

Example 2
エレベーターが故障中なので、階段をお使いください。
Erebētā ga koshouchuu na node, kaidan o o-tsukai kudasai.
The elevator is out of order, so please use the stairs.

Example 3
パソコンが故障したので、修理に出しました。
Pasokon ga koshou shita node, shuuri ni dashimashita.
My computer broke down, so I sent it in for repair.

Example 4
洗濯機が故障していて、全然動きません。
Sentakuki ga koshou shite ite, zenzen ugokimasen.
The washing machine is broken and won’t move at all.

Yuka

So if I drop my phone and the screen cracks and it won’t turn on — that’s 故障?

Rei

Exactly. A physical device that stops working because it’s damaged — that’s 故障. You’d say スマホが故障した and take it in for 修理 (repair). If the phone looks fine but an app is acting strangely, that’s a different word: 不具合.

What Does 不具合 Mean?

不具合（ふぐあい）is a broader, more polite term for “something not working correctly” or “a malfunction.” Unlike 故障, which implies physical damage to a device, 不具合 can apply to both hardware problems and software issues. It is the word Japanese companies use in official announcements, app update notes, and customer support responses.

If you read a notice that says 現在、システムに不具合が発生しております（げんざい、システムにふぐあいがはっせいしております）, that means “We are currently experiencing a system malfunction.” This polite, formal phrasing is standard in Japanese business and tech communication.

Common patterns: 不具合が発生する = a malfunction occurs / 不具合を報告する = to report a malfunction / 不具合が修正される = a malfunction is fixed

Example 1
現在、アプリに不具合が発生しており、ご不便をおかけしております。
Genzai, apuri ni fuguai ga hassei shite ori, go-fuben o okake shite orimasu.
We are currently experiencing a malfunction in the app and apologize for the inconvenience.

Example 2
このバージョンでいくつかの不具合が修正されました。
Kono bājon de ikutsuka no fuguai ga shuusei saremashita.
Several malfunctions were fixed in this version.

Example 3
商品に不具合があった場合は、お問い合わせください。
Shouhin ni fuguai ga atta baai wa, o-toiawase kudasai.
If there is a defect or malfunction with the product, please contact us.

Example 4
アプリの不具合を開発チームに報告しました。
Apuri no fuguai o kaihatsu chiimu ni houkoku shimashita.
I reported the app malfunction to the development team.

What Does エラー Mean?

エラー is a loanword from English “error,” but its meaning in Japanese tech contexts is specific: it refers to an error state or error message that appears on screen or is reported by a system. Think of it as what you see when something goes wrong — the red alert, the error code, the pop-up notification that tells you something is not right.

Common patterns: エラーが出る = an error appears / エラーコード = error code / 通信エラー = communication error / ログインエラー = login error / エラー画面 = error screen / エラーメッセージ = error message

Note that エラー does not imply the cause of the problem — the error could be caused by a bug, by a network issue, by wrong user input, or by a server outage. エラー is what the user observes.

Example 1
支払いをしようとしたら、エラーコード404が表示されました。
Shiharai o shiyou to shitara, eraa kōdo 404 ga hyouji saremashita.
When I tried to make a payment, error code 404 was displayed.

Example 2
通信エラーが発生したため、データを送信できませんでした。
Tsuushin eraa ga hassei shita tame, dēta o soushin dekimasen deshita.
A communication error occurred, so the data could not be sent.

Example 3
ログインしようとするたびに、エラーメッセージが出ます。
Roguin shiyou to suru tabi ni, eraa messēji ga demasu.
Every time I try to log in, an error message appears.

Example 4
エラー画面のスクリーンショットをサポートに送ってください。
Eraa gamen no sukurīnshotto o sapōto ni okutte kudasai.
Please send a screenshot of the error screen to support.

What Does バグ Mean?

バグ comes from the English word “bug” and means exactly the same thing in Japanese: a defect in software code that causes the program to behave incorrectly. It is primarily a technical term used by developers, but Japanese app users also use it casually — especially in app store reviews or social media posts when something clearly should not be behaving the way it does.

The key point: バグ implies the cause of the problem is in the code itself, not in the user’s actions or external conditions. When you say バグ, you are saying “the software is written incorrectly.”

Common patterns: バグを修正する = to fix a bug / バグがある = there is a bug / バグ報告 = bug report / バグが再現する = the bug reproduces / バグ修正パッチ = bug fix patch

Example 1
このゲームにはバグがあって、特定のアイテムを使うとフリーズします。
Kono gēmu ni wa bagu ga atte, tokutei no aitemu o tsukau to furīzu shimasu.
This game has a bug — using a specific item causes it to freeze.

Example 2
バグを見つけたら、開発者にバグ報告をしてください。
Bagu o mitsuketara, kaihatsusha ni bagu houkoku o shite kudasai.
If you find a bug, please submit a bug report to the developer.

Example 3
先週のアップデートでバグが修正されたはずなのに、まだ再現します。
Senshuū no appudēto de bagu ga shuusei sareta hazu na no ni, mada saigen shimasu.
The bug was supposed to be fixed in last week’s update, but it still reproduces.

Example 4
このバグは特定の端末でのみ発生するようです。
Kono bagu wa tokutei no tantai de nomi hassei suru you desu.
This bug seems to occur only on specific devices.

Yuka

So if my app shows an error message, is that バグ or エラー?

Rei

What you see is エラー — the message or code on screen. If that error is caused by a defect in the app’s code, then the underlying cause is バグ. Think of it this way: バグ is the reason, エラー is what appears. When reporting to support, describe the エラー (what you saw) and the steps that caused it — support will determine if it is a バグ.

故障 vs 不具合 — Broken Hardware vs General Malfunction

This is the comparison that trips up most learners. Both 故障 and 不具合 describe something “not working,” but they are used in very different situations.

Key contrast:

パソコンが故障した。
Pasokon ga koshou shita.
My computer broke down. (The hardware itself stopped working.)

パソコンのソフトウェアに不具合がある。
Pasokon no sofutowea ni fuguai ga aru.
There is a malfunction in the computer’s software. (Not physical damage — the software is misbehaving.)

Common mistake: Saying アプリが故障した (the app broke down) sounds unnatural — apps are not physical objects that break. Use アプリに不具合がある or アプリがうまく動かない instead.

エラー vs バグ — Error State vs Software Defect

Understanding the difference between エラー and バグ is important, especially if you need to write a bug report or contact a developer. The relationship is one of cause and effect: a バグ (software defect) can cause an エラー (error state), but not all errors come from bugs.

For example, if you enter the wrong password, you will see a ログインエラー (login error) — but there is no バグ. The error is caused by user input. On the other hand, if the correct password suddenly stops working even though nothing changed, that suggests a バグ is causing the ログインエラー.

User reporting エラー:
画面にエラーコード500が表示されて、サービスを利用できません。
Gamen ni eraa kōdo 500 ga hyouji sarete, sābisu o riyou dekimasen.
Error code 500 is displayed on screen and I cannot use the service.

Developer reporting バグ:
ユーザーが〇〇の手順を実行すると、バグが再現することを確認しました。
Yūzā ga ○○ no tejun o jikkou suru to, bagu ga saigen suru koto o kakunin shimashita.
We have confirmed that the bug reproduces when the user follows the ○○ steps.

User suspecting a バグ:
どうやら、特定の操作をするとバグが出るようです。
Dou yara, tokutei no sousa o suru to bagu ga deru you desu.
It seems that a bug appears when performing a certain operation.

Reporting Tech Problems in Japanese — Customer Support Phrases

Knowing the right vocabulary is only half the job. When you contact Japanese customer support or write a bug report, you also need the right sentence patterns. Here are practical templates for each type of problem.

Reporting 故障 (hardware breakdown):
〇〇が故障しているようです。修理をお願いできますか。
○○ ga koshou shite iru you desu. Shuuri o o-negai dekimasu ka.
It seems that ○○ has broken down. Could I request a repair?

Reporting 不具合 (malfunction — hardware or software):
アプリに不具合が発生しています。ご確認いただけますか。
Apuri ni fuguai ga hassei shite imasu. Go-kakunin itadakemasu ka.
A malfunction has occurred in the app. Could you please check?

Reporting エラー (error message):
ログインしようとすると、エラーコード〇〇が表示されます。スクリーンショットを添付します。
Roguin shiyou to suru to, eraa kōdo ○○ ga hyouji saremasu. Sukurīnshotto o tenpu shimasu.
When I try to log in, error code ○○ is displayed. I am attaching a screenshot.

Reporting バグ (software bug):
〇〇の操作をすると再現するバグがあります。再現手順を以下に記載します。
○○ no sousa o suru to saigen suru bagu ga arimasu. Saigen tejun o ika ni kisai shimasu.
There is a bug that reproduces when performing the ○○ operation. I will describe the steps to reproduce below.

Useful phrases for any support contact:

• スクリーンショットを添付します。(Sukurīnshotto o tenpu shimasu.) — I am attaching a screenshot.
• 再現手順（さいげんてじゅん）は以下のとおりです。— The steps to reproduce are as follows.
• 端末（たんまつ）の機種は〇〇です。— The device model is ○○.
• OSのバージョンは〇〇です。— The OS version is ○○.
• お手数ですが、ご確認いただけますか。(Otesuu desu ga, go-kakunin itadakemasu ka.) — I’m sorry to trouble you, but could you please check?

Other Tech Trouble Words Worth Knowing

Beyond the four main terms, several other words appear constantly when Japanese tech problems are discussed. Recognizing these will help you read error notifications, understand support responses, and follow developer updates.

障害（しょうがい）— System outage
障害 describes a large-scale service disruption, such as a server going down or a network-wide failure. It is more serious and broader than 不具合. Japanese companies post 障害情報（しょうがいじょうほう）= outage information on their status pages.

現在、サービス障害が発生しています。
Genzai, sābisu shougai ga hassei shite imasu.
A service outage is currently occurring.

不良（ふりょう）— Defective (physical product)
不良 refers to a defective physical item, especially a manufacturing defect. You might see 初期不良（しょきふりょう）= initial defect (a product that is defective right out of the box).

商品に初期不良があった場合は交換いたします。
Shouhin ni shoki furyou ga atta baai wa koukan itashimasu.
If the product has an initial defect, we will exchange it.

クラッシュ — Crash
Directly borrowed from English. アプリがクラッシュした = the app crashed. Very natural in casual and technical speech alike.

フリーズ — Freeze
Also directly borrowed. スマホがフリーズした = my smartphone froze. Often used alongside クラッシュ to describe the difference between a frozen screen and a full app crash.

ログインできない — Can’t log in
A very common complaint phrase. パスワードを入力してもログインできません = Even when I enter my password, I can’t log in.

Common Mistakes English Speakers Make

Even learners who know all four words sometimes use them incorrectly in practice. Here are the mistakes that come up most often.

1. Calling every problem バグ
In English, “bug” is used loosely for any tech annoyance. In Japanese, バグ specifically means a defect in software code. If your Wi-Fi dropped, that is not a バグ — it is a 通信エラー or possibly a 障害. Reserve バグ for situations where the software itself is written incorrectly.

2. Using 故障 for app problems
故障 is for physical objects. Saying アプリが故障した sounds as strange in Japanese as saying “my app physically broke” in English. Instead, say アプリに不具合がある or アプリがうまく動かない.

3. Confusing the error message with the bug
When you see an error message, what you are seeing is エラー. The underlying cause might be a バグ, but you cannot be certain. When reporting, describe the エラー (what you saw, including the code) and let the developer determine if a バグ is responsible.

4. Using 不具合 without enough detail
不具合 is polite and broad — useful precisely because of its vagueness in formal communication. But when writing a support ticket, follow it up with specifics: what happened, when, on which device, under what conditions.

5. Forgetting the エラーコード
Japanese support teams almost always ask for the エラーコード first. If you see a number or code on the error screen, copy it down and include it in your first message. エラーコード〇〇が表示されました (Error code ○○ was displayed) will speed up your support experience significantly.

6. Skipping 再現手順 when reporting a bug
A good bug report in any language includes how to reproduce the problem. In Japanese, this is called 再現手順（さいげんてじゅん）= reproduction steps. Without them, the developer cannot confirm or fix the バグ.

Decision Flowchart

Not sure which word to use? Work through this flowchart:

Is a physical device (phone, appliance, machine) broken and not working at all?
  YES → 故障（こしょう）
         e.g. スマホが故障した / 故障中
  NO  ↓

Is something (hardware or software) not behaving correctly?
  YES → 不具合（ふぐあい）
         e.g. アプリに不具合がある / 不具合が発生する
  NO  ↓

Do you see an error message, code, or alert on screen?
  YES → エラー
         e.g. エラーコードが表示された / ログインエラー
  NO  ↓

Is the likely cause a defect written into the software code?
  YES → バグ
         e.g. バグが再現する / バグ報告
  NO  ↓

Is the problem a large-scale service or network outage?
  YES → 障害（しょうがい）
         e.g. サービス障害が発生しています

Is the product defective from the factory or out of the box?
  YES → 不良 / 初期不良（ふりょう / しょきふりょう）

----------------------------------------------
Writing to support or developers?
  Physical device → 故障しているようです。修理をお願いできますか。
  App/system problem → 不具合が発生しています。ご確認いただけますか。
  Error message → エラーコード〇〇が表示されます。スクリーンショットを添付します。
  Software bug → 〇〇の手順でバグが再現します。再現手順を記載します。
----------------------------------------------

Quick Quiz

Fill in the blank with the correct word: 故障, 不具合, エラー, or バグ. Answers are below.

1. エレベーターが______中なので、使えません。
(The elevator is out of order, so it cannot be used.)

2. ログインしようとすると、______コード403が出ます。
(When I try to log in, error code 403 appears.)

3. 先週のアップデートでアプリの______が修正されました。
(The app malfunction was fixed in last week’s update.)

4. このゲームには特定のアイテムを使うとフリーズする______があります。
(There is a bug in this game that causes it to freeze when using a specific item.)

5. 洗濯機が______してしまったので、修理に出しました。
(My washing machine broke down, so I sent it in for repair.)

6. 現在、サービスに______が発生しており、一部機能をご利用いただけません。
(A malfunction is currently occurring in the service, and some features are unavailable.)

Answers:
1. 故障（こしょう）
2. エラー
3. 不具合（ふぐあい）
4. バグ
5. 故障（こしょう）
6. 不具合（ふぐあい）

Have you ever tried to explain a tech problem in Japanese — a broken phone, an app error, or a software bug? Which word did you use? Let us know in the comments!

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