What is the best way to translate the phrase on the fly? For example in:

I’ll try to capture the data on the fly.

The only translation that I was able to find was spontan, but I’m not sure if this translation is any good.

  • 1
    No, "spontan" quite directly translates to "spontaneously" (i.e. suddenly and without prior planning), it most probably does not express the same as what "on the fly" is supposed to say in your example. Commented Jul 29, 2015 at 20:21
  • 2
    It depends. On the fly csn be."nebenbei" or "beiläufig" if you emphase that you do it in parallel. Or "unverzüglich" to indicate the minimum delay in operation.
    – harper
    Commented Jul 29, 2015 at 20:22
  • @harper "beiläufig" fits perfectly. Thanks!
    – dmigo
    Commented Jul 29, 2015 at 20:28
  • 5
    @Chesheersky... "beiläufig" does totally NOT fit into the example you gave. Well, it does fit but it doesn't have the same meaning. What makes you think it does??
    – Emanuel
    Commented Jul 29, 2015 at 22:21
  • 3
    When it comes to technical descriptions, we usually simply say “on the fly” without translating it. But avoid it in formal papers if you suspect language watchmen to be within the audience…
    – Holger
    Commented Jul 30, 2015 at 11:14

7 Answers 7


I agree with Stephie's answer. However, there is a different non-technical use.

I'm going to give a presentation, but I don't need to prepare anything. I'll deal with questions on the fly.

That would be roughly translated to German like this:

Ich werde eine Präsentation halten, aber ich muss mich nicht vorbereiten. Fragen beantworte ich aus dem Stegreif.

Duden.de defines that as without preparation:

ohne Vorbereitung; improvisiert

Because that has come up, Stegreif without an h is indeed the correct spelling. Wikipedia.de explains nicely that it is an oldfashioned form of the contemporary word Steigbügel, which is stirrup in English. The things you put your feet in when riding a horse, and also what you use to lift yourself up when climbing on the horse.

The Gesellschaft für deutsche Sprache e. V. explains the German idiom Aus dem Stegreif as follows*.

[...] Ursprünglich war aus dem Stegreif rein wörtlich zu verstehen als ›etwas tun/vortragen, ohne vom Pferd zu steigen‹. Hieraus leitete sich die übertragene Bedeutung ab, die sich bis heute gehalten hat: ›etwas ohne Vorbereitung, ohne langes Überlegen tun oder vortragen, improvisieren‹. [...]

*) Cut marks [...] mine.

  • isn't it "Stehgreif"?
    – Zaibis
    Commented Jul 31, 2015 at 8:17
  • 1
    @Zaibis see my edit. It's not.
    – simbabque
    Commented Jul 31, 2015 at 8:25
  • 1
    While you give a good idiomatic expression and a lot of excellent detail, I fail to see how "aus dem Stegreif" would even remotely fit OP's context.
    – Stephie
    Commented Jul 31, 2015 at 18:02
  • @Stephie well I guess that was just an example the OP gave. They did say "for example". I agree that in the specific technical context you name your answer makes more sense. On the other hand in the comments of the question the OP agrees with a non-technical suggestion.
    – simbabque
    Commented Aug 4, 2015 at 6:43

In a technical context like your example on the fly is used in a sense of "without stopping (the machine / the current process / the data flow / ...)".
For these situations the German translation would be:

im laufenden Betrieb

(The other sense of "in a hurry" doesn't really fit your example - unless you want to say that you get the data real quick.)

  • Als wörtliche Übersetzung im tatsächlichen Sinne ja, aber nicht als Redensart.
    – Raphael
    Commented Jul 30, 2015 at 9:58
  • Im Vorbeigehen
  • im Vorübergehen
  • nebenbei.

Oder französisch/schachspielerisch:

  • en passant.

If you're working in an IT environment, you can write:

Ich werde versuchen die Daten während der Laufzeit aufzuzeichnen*.


Ich werde versuchen die Daten zur Laufzeit aufzuzeichnen.

*("aufzunehmen" would work, too)

Whereas "aufzeichnen/aufnehmen" is usually translated as "record" and "zur/während der Laufzeit" as "during runtime".

On a personal note: reading your sentence I rather understand that not you personally are recording the data but rather your application, device or something like that. So, a better way to phrase this would be (IMHO)

Data will be captured on the fly. - Die Daten werden zur Laufzeit aufgenommen.


Especially when you're talking about processing data, you could use "in Echtzeit" (in real-time, without latency).


on-the-fly can have many different translations. Here are a few that come to my mind:

  • Ad-hoc ("Ich beantworte die Rückfragen ad-hoc, ohne mich vorher darauf vorzubereiten." - I'll answer questions on-the-fly without preparation.)
  • Aus dem Stegreif (same context as ad-hoc)
  • In Echtzeit ("Die Daten werden in Echtzeit aufbereitet." - The data is prepared on-the-fly.)

The meaning your sentence uses is "in Echtzeit". Alternatives for the same context are "ohne Verzögerung" or "zur Laufzeit" or "im Betrieb". Literal back translations of these are in order "without delay", "during run-time" and "during operation" (As in "while the program still operates").

  • on the fly != in real-time . Only non-English speakers seem to have this idea. Commented Jul 31, 2015 at 15:54
  • 1
    @zeroflagL Could you then explain to me the precise characteristics of "on the fly data capturing" so I can learn the difference?
    – AlexR
    Commented Jul 31, 2015 at 16:27
  • While activity is ongoing. A flight recorder captures data (literally) on the fly. Getting data from the recorder does not happen on the fly. You do it when the machine is parking or has crashed. Playing a video of an animation happens in real-time, but the animation is not rendered on the fly. It has already been rendered before. Something can be done both on the fly and in real-time, but these are two distinct characteristics. Commented Jul 31, 2015 at 18:12
  • @zeroflagL Thanks, I think the flight recorder records in real-time (i.e. everything that happens is instantly recorded) So apparently on-the-fly has no implications on the duration of an individual computation or task - just that data is processed in a stream-like fashion. Real-time would then also imply short timing between the start of such a computation and the completion. This means to me that something done in real time is necessarily done on-the-fly?
    – AlexR
    Commented Aug 1, 2015 at 13:17

Ich werde versuchen, die Daten nebenher zu erfassen.

"Nebenher" something that's done alongside, without halting or hindering a simultaneous process.

  • Nebenher implies that you are doing sonething else and capturing the data as a side task. This has nothing to do with on-the-fly.
    – AlexR
    Commented Aug 1, 2015 at 13:19
  • @AlexR, Regarding the simultaneousness: Have a look at the discussion at dict.leo.org here and here.
    – michiindc
    Commented Aug 3, 2015 at 4:30

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